Fracture Blisters

Fracture blisters occur in about 3% of acute fractures requiring hospitalization, sometimes as early as 6 hours post fracture, with the majority appearing within 24–48 hours post fracture. Fracture blisters tend to occur in areas of tight skin without underlying muscle or adipose protection, such as the ankle, wrist, elbow, foot, and distal tibia. The blisters may be serous or hemorrhagic, with the latter representing more severe injury. Blisters usually heal by 2-3 weeks.

Fracture blisters are thought to be caused by skin strain during fracture leading to cleavage at the dermo-epidermal junction. Increased interstitial pressure from post-traumatic edema and/or local tissue hypoxia (from venous stasis/thrombosis or injured vessels) are thought to be contributing factors. Risk factors include high-energy trauma and conditions that predispose to poor wound healing (peripheral vascular disease, collagen vascular disease, hypertension, smoking, alcoholism, diabetes mellitus, and lymphatic obstruction).

Some surgeons prefer to leave blisters intact and delay surgical stabilization until the blisters have resolved, pointing to evidence of increased complications (chronic ulcers, infection, and prolonged hospitalization) when surgical incisions are through blisters. However, no consensus currently exists on the optimal treatment strategy.

Familiarity with fracture blisters is required for proper assessment of pre-operative CT. They may also be occasionally seen on radiographs (image at LearningRadiology.com)

References

Uebbing CM, Walsh M, Miller JB, Abraham M, Arnold C. Fracture blisters. West J Emerg Med. 2011 Feb;12(1):131-3.

Lauge-Hansen Classification

The Lauge-Hansen classification system describes ankle fractures as rotational-based injuries. The system was developed by applying rotational deforming forces to cadaveric ankles fixed at the tibia.

Four injury patterns are described based on the position of the foot at the time of injury (supination or pronation) and the direction of the deforming force (adduction or external rotation): supination-adduction, supination-external rotation, pronation-abduction, and pronation-external rotation. Each injury pattern, in turn, has different stages of injury.

Supination-Adduction

A supinated foot experiences forceful adduction without rotation. Stage I injury is tear of the lateral collateral ligaments (anterior talofibular, posterior talofibular, and calcaneofibular ligaments) and/or a transverse fracture of the fibula.

With increasing adduction, the talus is displaced medially, resulting in a vertical fracture of the medial malleolus (Stage II). Often, there is an impaction injury at the medial tibial plafond as well. The sine que non of this injury pattern is the vertical fracture of the medial malleolus, as the lateral component of the injury may be entirely ligamentous and radiographically occult.

Animations of supination-adduction injuries.

Supination-External Rotation

This is the most prevalent ankle fracture pattern. The supinated foot is exposed to an external rotation force, resulting in a shearing force to the fibula and an avulsive force to the medial osteoligamentous complex.

Four stages of injury have been described. Stage I injury represents rupture of the anterior tibiofibular ligament or avulsion fractures at one or both of its sites of attachment (Chaput tubercle of the tibia and Wagstaffe tubercle of the fibula).

A stage II injury includes the above plus an oblique fracture of the fibula. The fibular fracture is minimally displaced, oriented inferiorly in the postero-anterior direction, and located at the level of the syndesmosis.

Stage III injuries include the above injuries plus either a rupture of the posterior tibiofibular ligament or posterior malleolar fracture.

Stage IV injuries include the above plus a medial injury: either disruption of the deltoid ligament or a transverse fracture of the medial malleolus.

Radiographically a stage IV injury without posterior or medial malleolar fractures can resemble a stage II injury. Some advocate getting stress views to differentiate the two. Other findings that can help include anterior or posterior subluxation of the talus, shortening of the fibula (> 2 mm), and lateral subluxtion of the talus on unstressed views.

Animations of supination-external rotation injuries.

Pronation-Abduction

These injuries occur when a pronated ankle is exposed to an aBduction force. Three stages have been described. Stage I injuries are characterized by one or both of the following: transverse medial malleolus fracture and deltoid ligament rupture.

Further abduction results in a stage II injury, driving the talus laterally and resulting in rupture of the anterior and posterior tibiofibular ligaments or avulsion fractures at their attachment sites.

Stage III injuries represent further abduction forces causing a fracture of the fibula. The fracture usually occurs 5 cm to 7 cm above the tibiotalar joint and can be transverse, comminuted, or have a lateral butterfly component.

Stage II fractures that involve lateral ligamentous injury without an avulsion fracture can mimic isolated medial malleolar fractures or medial malleolar fractures due to direct trauma. Stress radiographs are helpful in this regard.

Animations of pronation-abduction injuries.

Pronation-External Rotation

These injuries occur when the pronated foot experiences an external rotation force. As in pronation-abduction injuries, the medial osteoligamentous structures are injured first. Four stages of injury have been described.

Stage I injuries involve either a transverse medial malleolar fracture or deltoid ligament rupture. Further external rotation results in a stage II injury: rupture of the anterior tibiofibular ligament or avulsion fracture at its attachment site (Chaput tubercle).

Stage III injuries involve injury to the syndesmosis and a typically spiral fracture of the fibula. A variant of the stage III pronation-external rotation injury is the Maisonneuve fracture.

Further external rotation is described as a stage IV injury, with fracture of the posterior malleolus or rupture of the posterior tibiofibular ligament.

Animations of pronation-external rotation injuries.

References

Lauge-Hansen N. Fractures of the ankle. II. Combined experimental-surgical and experimental-roentgenologic investigations. Arch Surg. 1950 May;60(5):957-85.

Posterior Intermalleolar Ligament

The posterior intermalleolar ligament, also known as the marsupial meniscus, is a small ligament in the posterior ankle. It is present in about 60%-80% of the population on autopsy, but can only be seen in about 20% of patients on routine MRI.

The posterior intermalleolar ligament has been erroneously considered as a synonym for the tibial slip of the posterior talofibular ligament. The tibial slip is a band of fibers connecting the posterior talofibular ligament to the medial malleolus, while the posterior intermalleolar ligament converges laterally to a bundle distinct from the posterior talofibular ligament.

Laterally, the fibers of the posterior intermalleolar ligament (red) are attached to the superior margin of the malleolar fossa of the fibula. The medial attachment site is much more variable, and includes the lateral border of the medial malleolar sulcus, the medial border of the medial malleolar sulcus through the septum between flexor digitorum longus and the tibialis posterior tendons, the posterior tibial cortex, the joint membrane covering the posterior process of the talus, and the floor of the flexor hallucis longus tunnel.

On MRI, the normal posterior intermalleolar ligament is a thick string or two or more fine parallel stripes on coronal images. It appears as a linear structure on axial images. On sagittal images, the ligament appears as scattered dots medially and as a thin flat or nodular structure laterally.

The posterior intermalleolar ligament may extend anteriorly, especially along its lateral extent, and give an appearance similar to that of a meniscus. This has been termed the marsupial meniscus due to its similarity to a structure found in marsupials. In marsupials, the talus has a lateral extension that serves as the receptive surface for the fibula, which is a significant weight-bearing component of the joint. A meniscus can be seen in these animals between the fibula and talus.

Entrapment and tearing of the posterior intermalleolar ligament can lead to posterior impingement syndrome, a phenomenon first described in ballet dancers with otherwise structurally normal ankles. The etiology is thought to be repetitive plantar flexion, causing intra-articular extension of the ligament and subsequent fraying and tearing.

MRI findings of posterior impingement syndrome due to posterior intermalleolar ligament pathology include a prominent posterior intermalleolar ligament as indicated by its presence in three different imaging planes and with a caliber comparable to other posterior ankle ligaments seen in the same imaging plane.

References

• Fiorella D, Helms CA, Nunley JA 2nd. The MR imaging features of the posterior intermalleolar ligament in patients with posterior impingement syndrome of the ankle. Skeletal Radiol. 1999 Oct;28(10):573-6.
• Lewis OJ. The joints of the evolving foot. Part I. The ankle joint. J Anat. 1980 May;130(Pt 3):527-43.
• Oh CS, Won HS, Hur MS, Chung IH, Kim S, Suh JS, Sung KS. Anatomic variations and MRI of the intermalleolar ligament. AJR Am J Roentgenol. 2006 Apr;186(4):943-7.
• Rosenberg ZS, Cheung YY, Beltran J, Sheskier S, Leong M, Jahss M. Posterior intermalleolar ligament of the ankle: normal anatomy and MR imaging features. AJR Am J Roentgenol. 1995 Aug;165(2):387-90.

Advanced Imaging Technology at Airports

There was an interesting discussion in this month's Radiology about airport scanners (advanced imaging technology, or AIT). Two main technologies currently exist: Backscatter X-ray (ionizing radiation) and millimeter-wave (non-ionizing radiation).

Backscatter X-ray Systems

These devices transmit x-rays to passengers (depending on the manufacturer, the x-rays are either 50 kVp or 120 kVp) and detect reflected radiation. Some of the x-rays penetrate deep into the body (see below) and some bounce off the skin. The posteroanterior and anteroposterior images are obtained mainly from the reflected photons.

Three manufacturers currently make these devices: Rapiscan (Secure 1000), American Science and Engineering (Smartcheck), and Tek84 (AIT84 Body Scanner and Castscope, the latter designed for examining casts, bandages, and artificial limbs).

Given the public concern about radiation and privacy, more thought could have been put into naming these devices. Rapiscan raises the spectre of violation, the AIT84 brings to mind George Orwell's 1984, and Castscope manages to raise associations with both castration and colonoscopy.

Public fears and unfortunate names aside, the estimated radiation from these devices is pretty low. Skin dose estimates range from 0.7 μGy to 2.5 μGy and effective dose estimates from 0.015 μSv to 0.9 μSv. By way of comparison, we get an effective dose of about 0.04 μSv/minute just by flying in an airplane.

A common misconception is that photons from backscatter devices do not penetrate deep into the body (here's one from an ACR press release). While seemingly reassuring at first consideration, the implication of this misconception is that skin doses can be many times higher than the effective dose to the entire body. This misconception is the result of confusion of dose penetration with imaging penetration, the former reflecting the behavior of the photons in the body and the latter describing the photons used for image creation (more here).

The penetration of the photons into the body does raise concern about fetal dose. However, a scan delivering an effective dose of 0.25 μSv to the mother is estimated to deliver only about 0.12 μSv to the uterus.

Millimeter-Wave Systems

Another system used in airports makes use of non-ionizing, millimeter-wave radiation. These come in active and passive varieties. Active scanners direct millimeter-wave energy at the passenger, while passive systems detect energy naturally emitted from the body and concealed objects. The data is then analyzed and reconstructed to generate a 3-dimensional holographic image (as opposed to the planar images generated by the backscatter devices).

L3 Security and Detection Systems manufactures the ProVision system currently used by the TSA.

References

• Brenner DJ. Are x-ray backscatter scanners safe for airport passenger screening? For most individuals, probably yes, but a billion scans per year raises long-term public health concerns. Radiology. 2011 Apr;259(1):6-10.
• Zanotti-Fregonara P, Hindié E, Brenner DJ. Radiation Risk from Airport X-ray Backscatter Scanners: Should We Fear the Microsievert? Radiology. 2011 Oct;261(1):330-1.

Sagittal Balance and the Flat Back Syndrome

Sagittal balance refers to the position of the head in relation to the pelvis and is largely determined by the kyphosis of the thoracic spine and the lordosis of the lumbar spine.

Formal radiographic assessment is done using a standing full-length lateral radiograph obtained with extension at the hips and knees. The C7 vertebral body and the hip joint should be visualized. The optimal position of the arms has been debated. Having the arms at the side would obviously be the most natural position for the patient; however, this limits evaluation of the spine. Holding the arms in front of the patient (sleepwalker style) has been shown to result in posterior shift of the sagittal vertical axis (see below). A compromise seems to be flexion at the shoulder between 30º - 45 º with the arms holding on to a support.

A line is then drawn perpendicular to the ground (plumb line) from the center of the C7 vertebral body to the pelvis. This approximates the sagittal vertical axis. The distance of this line to the posterosuperior aspect of the S1 vertebral body is the sagittal vertical axis offset, sometimes incorrectly abbreviated to sagittal vertical axis. The normal range for the sagittal vertical axis offset has not been agreed on and may be anywhere between 2.5 cm and 5.0 cm.

• Negative sagittal imbalance: Plumb line falls behind the posterosuperior corner of the S1 vertebral body.
• Neutral sagittal balance: Plumb line intersects the posterosuperior corner of the S1 vertebral body.
• Positive sagittal imbalance: Plumb line falls in front of the posterosuperior corner of the S1 vertebral body.

Flat back syndrome (also known as flatback or flat-back syndrome refers to the loss of normal lumbar lordosis. When segmental, there is loss of lumbar lordosis or kyphosis with preservation of neutral sagittal balance (type 1 flat back syndrome). Type 2 (global or classic) flat back syndrome, on the other hand, represents loss of lumbar lordosis with significant fixed positive sagittal imbalance.

Flat back syndrome is most commonly iatrogenic. Patients present with a forward tilt of the trunk, inability to stand erect, muscular pain in the upper back and lower cervical area, and thigh pain from chronic hip flexion and knee bending.

Formal radiographic assessment makes use of the plumb line on standing lateral radiographs, as described above. The plumb line can fall within 2 cm of the anterior aspect of the sacrum in patients without scoliosis or in those with idiopathic scoliosis who have not undergone corrective surgery.

The images below are from a patient with a history of discectomy and multilevel laminectomy at an outside facility. The patient's baseline images show a loss of lumbar lordosis (A). She subsequently had surgery with an attempt to re-establish some lumbar lordosis (B). The lateral upright radiograph (C) is a great example of bad technique. The arms are flexed at 90º and C7 is not seen.

References

• Harding IJ. Understanding sagittal balance with a clinical perspective. Eur J Phys Rehabil Med. 2009 Dec;45(4):571-82.
• Lu DC, Chou D. Flatback syndrome. Neurosurg Clin N Am. 2007 Apr;18(2):289-94.
• Vialle R, Levassor N, Rillardon L, Templier A, Skalli W, Guigui P. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005 Feb;87(2):260-7.

Treacher Collins Syndrome

Currently traveling through England and Wales, where we ran into a TV show on BBC Three on a young man with Treacher Collins syndrome. Apologies for the brevity and tardiness of posts.

Treacher Collins syndrome, named for Edward Treacher Collins (hence, no hyphen between Treacher and Collins), is an autosomal dominant disorder that results from embryologic abnormalities that affect the second and third brachial arches. The condition has variable penetrance and phenotypic expression. The majority of cases (60%) are sporadic, with 40% presenting with a family history of disease.

Also known as mandibulofacial dysostosis, Treacher Collins syndrome is characterized by anomalous (often bilateral and symmetric) development of multiple structures arising from the second and third brachial arches. These problems can be surgically corrected.

• Eyelids: Antimongoloid slanting of the eyes (outer canthus is lower than the inner canthus), shortened palpebral fissures, lower lid colobomas, absent eyelashes. Colobomas are usually corrected during the 1st year of life.
• Zygomatic bones: Small or absent zygomatic arches. Usually corrected between 4–10 years of age.
• Maxilla: Narrow or overprojected maxilla, elevated or narrow palate.
• Mandible: Hypoplasia, dental malocclusion, retruded chin. Usually corrected between 4–10 years of age.
• Nose: Broad or protruded.
• External ear: External auditory canal anomalies (stenotic or atretic in >80% of patients), pinna deformity. Can result in conductive hearing loss. Pinna repair is usually after the age of 6 (requires adequate costal cartilage development).
• Middle ear: Middle ear malformations. Can result in conductive hearing loss.
• Mouth: Microstomia.

References

• Katorza E, Nahama-Allouche C, Castaigne V, Gonzales M, Galliani E, Marlin S, Jouannic JM, Rosenblatt J, le Pointe HD, Garel C. Prenatal evaluation of the middle ear and diagnosis of middle ear hypoplasia using MRI. Pediatr Radiol. 2011 May;41(5):652-7.
• Lowe LH, Booth TN, Joglar JM, Rollins NK. Midface anomalies in children. Radiographics. 2000 Jul-Aug;20(4):907-22.

Synovial Fluid Circulation in the Hip

Traveling through England and Wales with apologies for the tardiness and brevity of posts.

Synovial tissue in the hip is predominantly located in the peripheral compartment; however, the central compartment, where the articular cartilage of the femoral head and acetabulum reside, is where the lubrication of the synovial fluid is needed.

The peripheral compartment consists of proximal and distal zones. These two zones are separated from each other by the zona orbicularis, the deep circular fibers of the ischiofemoral ligament.

On hip flexion, the transverse ligament separates from the femoral head and synovial fluid flows from the peripheral compartment into the acetabular notch (cotyloid fossa). On hip extension, fluid passes across the articular surface and pools adjacent to the labrum and in the labro-chondral sulcus. The movement of the zona orbicularis serves as a bellows to drive synovial fluid, and the labrum acts as a reservoir to delay return of fluid to the peripheral compartment.

References

Field RE, Rajakulendran K. The labro-acetabular complex. J Bone Joint Surg Am. 2011 May;93 Suppl 2:22-7.

Melanoma Metastases to Bone

Skeletal metastases from malignant melanoma are found during autopsy in ~25% to 50% of patients who die of the disease. Radiolography and scintigraphy are much less sensitive, with metastatic lesions detected in less than 10% of patients. CT is slightly better, detecting axial skeletal metastases in about 15% of patients with melanoma.

Radiographic findings, when present, are nonspecific. Until cortical destruction has occurred, most medullary metastases are radiographically occult. Most skeletal metastases from melanoma progress rapidly. The vast majority of the lesions are osteolytic, although sclerotic or mixed lesions can also occur. The margins of the lesions are usually poorly defined. Periosteal reaction is uncommon, and when present, is minimal.

The CT findings in bony metastases from melanoma are nonspecific. The majority of lesions are osteolytic, slightly expansile, and occasionally associated with soft-tissue masses. The lesions may rarely be sclerotic, but tumor matrix is not generally seen in lytic lesions in the axial skeleton.

MRI findings are not as well described. A report of spinal metastases from melanoma described increased T1 signal intensity in bone.

The images above show an FDG-avid lytic lesion in the right side of the sacrum. As you can see, the lesion can be subtle, stressing the importance of careful evaluation of images in bone windows in these patients.

References

• Fon GT, Wong WS, Gold RH, Kaiser LR. Skeletal metastases of melanoma: radiographic, scintigraphic, and clinical review. AJR Am J Roentgenol. 1981 Jul;137(1):103-8.
• McMenamin DS, Stuckey SL, Potgieter GJ. T1 hyperintense vertebral column melanoma metastases. AJNR Am J Neuroradiol. 2007 Oct;28(9):1817-8.
• Patten RM, Shuman WP, Teefey S. Metastases from malignant melanoma to the axial skeleton: a CT study of frequency and appearance. AJR Am J Roentgenol. 1990 Jul;155(1):109-12.

Extramammary Paget Disease

Extramammary Paget disease is an uncommon malignant neoplasm that occurs in areas with high concentrations of apocrine glands such as the genitoanal area (most common, and usually in women), axilla, eyelids, the oral cavity, and the exernal auditory canal. Patients present with an erythematous, eczematoid, slowly spreading plaque and commonly have interactable pruritus.

As in Paget disease of the nipple, there is intraepithelial (usually intraepidermal) infiltration by neoplastic cells showing glandular differentiation. However, while the origin of the neoplastic cells in Paget disease of the nipple are well-known (in situ or invasive ductal carcinoma in the underlying breast tissue), the origin of neoplastic cells in extramammary Paget disease is somewhat controversial.

The neoplastic cells in extramammary Paget disease are thought to arise from the epidermis (primary form), either from the intraepidermal portions of apocrine gland ducts or from pluripotent keratinocyte stem cells. The secondary form refers to cases where there is an underlying neoplasm in a dermal adnexal gland or a local organ with contiguous epithelium. The word adnexa (appendage) in this context refers to the appendages of skin (hair, arrector pili, sebaceous glands, apocrine or eccrine glands, and nails).

References

• Lloyd J, Flanagan AM. Mammary and extramammary Paget's disease. J Clin Pathol. 2000 Oct;53(10):742-9.
• Krause W, Krisp A, Hörster S, Hoffmann R. Genital Paget's disease in a man. Eur J Dermatol. 2006 Jan-Feb;16(1):75-8.

Westcott and Franseen Biopsy Needles

Fine needle aspiration biopsies are most commonly performed with Chiba, Franseen, and Westcott needles.

The Chiba needles come in sizes between 25-G and 18-G. These needles have beveled tips on both the stylet (pink) and outer cannula (blue). We typically use the 18-G Chiba needles for obtaining access to the lesion, and perform the fine needle aspiration with 22-G Franseen or Westcott needles.

The Franseen needle has multibeveled cutting edges on both the inner stylet (pink) and outer cannula (blue). The Franseen needles come in sizes between 22 G to 14 G.

The Westcott needle has a beveled tip and a notched outer cannula (blue). The side notch creates a second cutting edge and allows for aspiration of more material; however, the volume is often limited by the smaller sizes these needles come in (see below). The side notch is 2 mm in length and begins approximately 3 mm from the tip of the needle. The Westcott needles come in sizes between 22 G to 20 G.

Note: The images are highly stylized and may not be 100% accurate. You can use an image search to see manufacturers' versions of these needles (Chiba, Franseen, and Westcott)

References

Beall DP. Chapter 3: Common Procedures. in Radiology Sourcebook: A Practical Guide for Reference and Training. Humana Press (2002). Totowa, NJ. pp 17-18.

Lymphomatous Involvement of the Adrenal Glands

Lymphomatous involvement of the adrenal glands occurs in less than 5% of patients with non-Hodgkin lymphoma. 50% of these patients have bilateral involvement. Other types of lymphoma involve the adrenal glands even less frequently. Involvement is most commonly secondary.

Patients may present with adrenal insufficiency.

The most common imaging finding is nonspecific unilateral or bilateral enlargement of the adrenal glands. Adenopathy in the abdomen and elsewhere may suggest the diagnoosis. Early on, the shape of the adrenal gland may be preserved, mimicking adrenal hypertrophy or hyperplasia. Washout characteristics are similar to those of other adrenal malignancies.

FDG avidity of the adrenal glands on PET imaging tends to follow that of other involved areas. FDG upatke, however, may not be a reliable indicator of disease activity in certain types of lymphoma (e.g., marginal zone and peripheral T-cell lymphomas) and may be low in low-grade lymphomas.

On MRI, the lesions are heterogeneously T1-hypointense and T2-hyperintense and demonstrate progressive contrast enhancement.

The images above are from a patient with diffuse large B-cell lymphoma and show multiple adrenal lesions bilaterally. The lesions are FDG avid. Biopsy showed lymphomatous involvement.

References

• Blake MA, Cronin CG, Boland GW. Adrenal imaging. AJR Am J Roentgenol. 2010 Jun;194(6):1450-60.
• Leite NP, Kased N, Hanna RF, Brown MA, Pereira JM, Cunha R, Sirlin CB. Cross-sectional imaging of extranodal involvement in abdominopelvic lymphoproliferative malignancies. Radiographics. 2007 Nov-Dec;27(6):1613-34.

Calcified Mesenteric Masses: Differential Diagnosis

• Calcified metastatic implants: Ovarian carcinoma, mucinous colon carcinoma, or gastric carcinoma.
• Carcinoid: Enhancing soft-tissue mass with surrounding radiating bands (fibrotic proliferation and desmoplastic reaction due to serotonin). 70% contain calcifications. Adjacent small bowel loops can be thickened (due to tumor infiltration or ischemia) or angulated.
• Chronic sclerosing mesenteritis (shown above): Sclerosing mesenteritis is a rare inflammatory condition that affects the fat at the root of the mesentery with variable amounts of inflammation, fatty necrosis, and fibrosis. The chronic phase is also known as retractile mesenteritis and is characterized by fibrosis and a soft-tissue mass, with or without dystrophic calcifications.
• Amyloidosis: An unusual presentation of systemic amyloidosis is one with mesenteric and/or omental infiltration, typically with coarse dystrophic calcifications.
• Peritoneal echinococcosis: Almost always due to hepatic involvement and subsequent seeding from spontaneous or iatrogenic rupture. Suggestive features are cysts with calcific rims.

References

• Pickhardt PJ, Bhalla S. Unusual nonneoplastic peritoneal and subperitoneal conditions: CT findings. Radiographics. 2005 May-Jun;25(3):719-30.
• Sheth S, Horton KM, Garland MR, Fishman EK. Mesenteric neoplasms: CT appearances of primary and secondary tumors and differential diagnosis. Radiographics. 2003 Mar-Apr;23(2):457-73.

Osteolytic Lesions in Prostate Cancer

While the majority of metastases from prostate adenocarcinoma are sclerotic, about 5% can be osteolytic. Mixed osteolytic and sclerotic lesions can also be seen. The uncommon neuroendocrine tumors of the prostate also produce osteolytic lesions.

Regardless of pathology, both bone resorption and bone formation can be seen in metastatic lesions from prostate cancer, with the radiographic appearance reflecting the dominant process. Sclerotic metastases are the result of stimulation of osteoblasts or inhibition of osteoclasts or both by cancer cells, whereas lytic metastases are the result of stimulation of osteoclasts or inhibition of osteoblasts or both by cancer cells.

References

• Conti G, La Torre G, Cicalese V, Micheletti G, Ludovico MG, Vestita GD, Cottonaro G, Introini C, Cecchi M. Prostate cancer metastases to bone: observational study for the evaluation of clinical presentation, course and treatment patterns. Presentation of the METAURO protocol and of patient baseline features. Arch Ital Urol Androl. 2008 Jun;80(2):59-64.
• Guise TA, Mohammad KS, Clines G, Stebbins EG, Wong DH, Higgins LS, Vessella R, Corey E, Padalecki S, Suva L, Chirgwin JM. Basic mechanisms responsible for osteolytic and osteoblastic bone metastases. Clin Cancer Res. 2006 Oct 15;12(20 Pt 2):6213s-6216s.
• Logothetis CJ, Lin SH. Osteoblasts in prostate cancer metastasis to bone. Nat Rev Cancer. 2005 Jan;5(1):21-8.
• Roodman GD. Mechanisms of bone metastasis. N Engl J Med. 2004 Apr 15;350(16):1655-64.

Lymphatic Drainage in Penile Cancers

The pattern of lymphatic spread in penile carcinomas depends on the location of the primary lesion.

• Skin of the penis and prepuce: Lymphatics drain primarily into the superficial inguinal lymph nodes (pink arrows).
• Glans penis: Lymphatics drain into the deep inguinal (blue arrows) and external iliac lymph nodes. May also drain into the superficial inguinal lymph nodes.
• Erectile tissue: Lymphatics drain into the internal iliac lymph nodes. Metastasis to pelvic lymph nodes is uncommon in the absence of inguinal lymphatic involvement.
• Penile urethra : Lymphatics drain into the internal iliac lymph nodes. Metastasis to pelvic lymph nodes is uncommon in the absence of inguinal lymphatic involvement.

The superficial inguinal lymph nodes (pink arrows) are found along the anterior and medial aspects of the saphenofemoral junction between the Scarpa fascia and the fascia lata. The deep inguinal lymph nodes (blue arrows) are medial and lateral to the femoral vein and deep to the fascia lata and receive afferent lymphatics from the superficial nodes.

Bilateral lymphadenopathy can be seen with a unilateral tumor because of communication between left and right lymphatic vessels.

References

• Paño B, Sebastià C, Buñesch L, Mestres J, Salvador R, Macías NG, Nicolau C. Pathways of lymphatic spread in male urogenital pelvic malignancies. Radiographics. 2011 Jan-Feb;31(1):135-60.
• Singh AK, Saokar A, Hahn PF, Harisinghani MG. Radiographics. 2005 Nov-Dec;25(6):1629-38. Imaging of penile neoplasms. Mehta A, Bansal SC. Diagnosis and Management of Cancer. Chapter 32: Cancer of the penis. In Diagnosis and Management of Cancer. Jaypee Brothers Publishers, 2004.

OMERACT Definitions

OMERACT (Outcome Measures in Rheumatoid Arthritis Clinical Trials) has a set of consensus definitions for important joint pathologies and an MRI scoring system called the RAMRIS (RA-MRI Scoring).

The definitions and scoring system are focused on the wrist and metacarpophalangeal joints because of their frequent involvement in rheumatoid arthritis and the large amount of MRI data on these joints.

Atlases have been published for the wrist and the metacarpophalangeal joints and should be used for guidance and calibration.

The definitions are as follows:

• Assessed bone volume: Used for scoring bone erosions (see below). In the long bones, the assessed bone volume is from the articular surface (or its best estimated position) to a depth of 1 cm. For the carpal bones, the assessed bone volume is the whole bone.
• MRI bone edema: A lesion, alone or surrounding an erosion or other bone abnormality, within the trabecular bone, with ill-defined margins and fluid signal.
  
  Each bone is scored separately. The scale is from 0–3 based on the proportion of bone with edema. 0: no edema; 1: 1%–33% of bone is edematous; 2: 34%–66% of the bone is edematous; 3: 67%–100% of bone is edematous.
• MRI bone erosion: A sharply marginated bone lesion, with correct juxtaarticular localization and typical signal characteristics, which is visible in 2 planes with a cortical break seen in at least one plane.
  
  Typical signal characteristics on T1-weighted images: loss of normal low signal intensity of cortical bone and loss of normal high signal intensity of trabecular bone. Quick post-gadolinium enhancement suggests presence of active, hypervascularized pannus tissue in the erosion.
  
  Each bone is scored separately. For the wrists: carpal bones, distal radius, distal ulna, and metacarpal bases. For the metacarpophalangeal joints: metacarpal heads and phalangeal bases.
  
  The scale for scoring is from 0–10. The score is based on the proportion of eroded bone compared to the assessed bone volume (see above), judged on all available images. 0: no erosion; 1: 1%–10% of bone eroded; 2: 11%–20%, etc.
• Synovitis: An area in the synovial compartment that shows above normal post-gadolinium enhancement with a thickness greater than the width of the normal synovium.
  
  Synovitis is assessed in three wrist regions (the distal radioulnar joint, the radiocarpal joint, and the intercarpal and carpometacarpal joints) and in each metacarpophalangeal joint. The scale is 0–3 (0: normal, 1: mild, 2: moderate, 3: severe).
  
  The first carpometacarpal joint and the first metacarpophalangeal joint are not scored.

References

• Conaghan P, Bird P, Ejbjerg B, O'Connor P, Peterfy C, McQueen F, Lassere M, Emery P, Shnier R, Edmonds J, Østergaard M. The EULAR-OMERACT rheumatoid arthritis MRI reference image atlas: the metacarpophalangeal joints. Ann Rheum Dis. 2005 Feb;64 Suppl 1:i11-21.
• Ejbjerg B, McQueen F, Lassere M, Haavardsholm E, Conaghan P, O'Connor P, Bird P, Peterfy C, Edmonds J, Szkudlarek M, Genant H, Emery P, Østergaard M. The EULAR-OMERACT rheumatoid arthritis MRI reference image atlas: the wrist joint. Ann Rheum Dis. 2005 Feb;64 Suppl 1:i23-47.
• Østergaard M, Edmonds J, McQueen F, Peterfy C, Lassere M, Ejbjerg B, Bird P, Emery P, Genant H, Conaghan P. An introduction to the EULAR-OMERACT rheumatoid arthritis MRI reference image atlas. Ann Rheum Dis. 2005 Feb;64 Suppl 1:i3-7.

Calyceal Diverticula on FDG PET

Calyceal diverticula are potential pitfalls in interpreting FDG-PET studies. They can appear as foci of increased uptake on PET and mimic hypermetabolic renal lesions. The increased FDG activity, however, is just due to renal excretion into the calyceal diverticulum. This can be confirmed with contrast-enhanced CT during the renal excretory phase.

The patient above presented for staging of lung carcinoma and was found to have a focus of increased activity in the right kidney. Correlation with portal venous and delayed CT imaging, however, reveals the typical appearance of a calyceal diverticulum: fluid-attenuation structure that fills in with contrast on excretory phase images.

References

Kavanagh JJ, Gordon L, Curry NS, Ravenel JG. Calyceal diverticulum mimicking a renal tumor on FDG PET imaging. Clin Nucl Med. 2006 May;31(5):301-2.

Virchow's Node

In 1849, Rudolf Ludwig Karl Virchow, noted the involvement of remote lymph nodes in intraabdominal cancers. 40 years later, Troisier, reporting several cases of intra-abdominal malignancy where supraclavicular lymph nodes were the only external indication of cancer, coined the term Virchow's node to describe this finding. In current usage, Virchow's node refers to a left supraclavicular lymph node that is the harbinger of an abdominal malignancy. It should be remembered that inflammatory and infectious abdominal processes can also lead an enlarged left supraclavicular lymph nodes.

The thoracic duct drainage has been implicated for the involvement of left supraclavicular lymph nodes. The thoracic duct drains the left jugular, left subclavian, and left mediastinal lymph nodes superiorly. Inferiorly, the thoracic duct drains the intercostal lymphatics, and via the cisterna chyli, the lower intercostal, gastric, superior mesenteric, inferior mesenteric, lumbar, and internal and external iliac lymphatics.

The left supraclavicular lymph nodes drain into the thoracic duct via short lymphatic channels draining into the left jugular lymphatics. Reflux into the left supraclavicular lymph nodes from the thoracic duct is relatively easy, occurs in half of patients with unobstructed lymphatic drainage, and is the proposed etiology of Virchow's node.

The right-sided lymphatic drainage, on the other hand, is not from the abdomen, being predominantly from the right subclavian, right mediastinal, and right jugular vessels.

The case above is from a patient with endometrial carcinoma who had metastases to bilateral supraclavicular lymph nodes. Retroperitoneal adenopathy can also be seen. Biopsy of a left supraclavicular lymph node yielded cells similar to the patient's primary malignancy.

References

• Cervin JR, Silverman JF, Loggie BW, Geisinger KR. Virchow's node revisited. Analysis with clinicopathologic correlation of 152 fine-needle aspiration biopsies of supraclavicular lymph nodes. Arch Pathol Lab Med. 1995 Aug;119(8):727-30.
• Zeidman I. Experimental studies on the spread of cancer in the lymphatic system. III. Tumor emboli in thoracic duct; the pathogenesis of Virchow's node. Cancer Res. 1955 Dec;15(11):719-21.

MRI and Scaphoid Viability

Determining the viability of scaphoid fracture fragments is important in surgical planning, with some surgeons electing vascularized bone grafts when a non-viable fragment is suspected. Contrast-enhanced MRI would, at first glance, seem to be a good way of assessing viability prior to surgery; however, there are conflicting data on this matter.

A recent study by Donati and colleagues in Radiology looked at the performance of MRI in detecting non-viable scaphoid poles in 28 patients. They defined viability based on intraoperative findings: if the surface of the proximal scaphoid pole remained pale after débridement, with lack of surface bleeding and no bleeding after removal of the surgical tourniquet, the proximal pole was considered to be nonviable.

They found that while 90% of viable scaphoid poles had enhancement, approximately half of non-viable scaphoid poles had at least some enhancement. The authors found that subjective enhancement by itself was not an accurate predictor of scaphoid viability. Objective assessment of viability with dynamic enhanced MR imaging fared even worse for detection of scaphoid non-viability.

They attribute the enhancement in non-viable fragments to the presence of fibrovascular tissue in the setting of avascular necrosis, as well as patchy areas of vascularized bone.

Some have advanced the use of non-contrast signal characteristics for determining viability, with the finding of low signal on T1- and T2-weighted images as suggestive of poor vascularity. Donati and colleagues, however, found that the vast majority of both viable and non-viable scaphoid poles has low or intermediate signal on T1-weighted images, likely related to callus formation in both groups of patients. They also found that the vast majority of both viable and non-viable scaphoid poles had hyperintense signal on fluid-sensitive sequences, possibly due to immature callus, blood vessels, bone marrow edema, and/or bone marrow fibrosis and bleeding.

Overall, Donati and colleagues found sensitivities in the range of 60%, negative predictive values in the range of 70% - 74%, and a specificity of ~90% for detection of scaphoid necrosis when using pre- and post-contrast images.

While contrast-enhanced MRI is the best we can do at this point for assessing scaphoid viability, we should keep its low sensitivity and low negative predictive value in mind when interpreting images. The high specificity of contrast-enhanced MRI, on the other hand, means that we can count on positive findings of low signal intensity on T1- and T2-weighted images and absent or small-volume enhancement as evidence of non-viability.

References

• Cerezal L, Abascal F, Canga A, García-Valtuille R, Bustamante M, del Piñal F. Usefulness of gadolinium-enhanced MR imaging in the evaluation of the vascularity of scaphoid nonunions. AJR Am J Roentgenol. 2000 Jan;174(1):141-9.
• Donati OF, Zanetti M, Nagy L, Bode B, Schweizer A, Pfirrmann CW. Is Dynamic Gadolinium Enhancement Needed in MR Imaging for the Preoperative Assessment of Scaphoidal Viability in Patients with Scaphoid Nonunion? Radiology. 2011 Sep;260(3):808-16.

Giant Cell Tumor of Bone: The Hands

Between 2%-4% of giant cell tumors of bone affect the hand, with the majority of these involving the metacarpals.

Compared to patients with giant cell tumors in more common locations like the distal femur, proximal tibia, and distal radius, patients with giant cell tumors of the hand:

• tend to be slightly younger,
• are more likely to have higher grade lesions, with 60% presenting as Campannaci grade 3, and
• are more likely to have multicentric disease,

Radiographic findings are similar to giant cell tumor elsewhere in the body: Expansile, lytic lesion involving the epiphysis and metaphysis. Pseudotrabeculations can be seen peripherally. About 10% have a sclerotic border

In contrast to lesions elsewhere, giant cell tumors in the hand tend to be higher grade, with more than half demonstrating cortical destruction. They are also more likely to be central in location (85%), likely due to the smaller volume of the involved bone.

MRI findings are similar to giant cell tumors elsewhere. In more than 50% of cases, MRI will show very low signal intensity on all pulse sequences due to chronic hemosiderin deposition, but the appearance is variable. Fluid-fluid levels can be seen in about 15% of cases, and a low signal intensity rim can be seen in some cases. Early enhancement and washout are typical.

Differential considerations include:

• Enchondroma: Usually asymptomatic. Commonly have a sclerotic border. Stable over time. More likely to occur in the phalanges (unlike giant cell tumors, which tend to occur in the metacarpals).
• Aneurysmal bone cyst: More common in skeletally immature patients.
• Giant-cell reparative granuloma: May also be expansile and lytic with cortical destruction.
• Sarcoidosis:
• Brown tumor: Can histologically mimic giant cell tumor of bone. Look for other radiographic evidence of hyperparathyroidism.
• Fibrous dysplasia: Usually polystotic in the hand.
• Osteomyelitis: Especially tuberculosis with the spina ventosa appearance.

References

James SL, Davies AM. Giant-cell tumours of bone of the hand and wrist: a review of imaging findings and differential diagnoses. Eur Radiol. 2005 Sep;15(9):1855-66.

Osteochondral Lesions of the Talus

Osteochondral lesions of the talus (OLT) involve the articular surface and/or the subchondral region of the talus. Osteochondral lesion of the talus encompasses older terms such as transchondral fracture, osteochondral fracture, osteochondritis dissecans, and talar dome fracture.

Most osteochondral lesions of the talus are thought to represent the chronic phase of compressed or avulsed talar dome fractures due to acute trauma or repetitive microtrauma. Genetic, metabolic, and endocrine etiologies account for a minority of cases.

The lateral surface of the talus is involved in 40% of cases. Osteochondral lesions here tend to be thin and wafer-shaped and located in the anterior to mid talar dome, as seen in the images above. About 95% of cases are caused by trauma, most commonly an inversion injury accompanied by dorsiflexion of the foot and internal rotation of the talus. The mechanism of injury is compression and shear by the medial margin of the fibula.

The medial surface of the talus is involved in 60% of cases. Medial injuries tend to be cup-shaped and deeper than lateral injuries and tend to be located posteriorly. They can be caused by an inversion injury accompanied by plantarflexion of the foot and external rotation of the talus, although the association with trauma is not as strong as that seen in lateral injuries. Medial lesions can be bilateral in up to 30% of cases.

Isolated bone injuries result in a subchondral fracture without cartilage injury. This was the case with the patient shown above. When both cartilage and bone are affected, a displaced osteochondral fragment can result. Classification systems have been developed for these ends of the spectrum and everything in between. These schemes can be based on radiography, CT, MRI, or surgical findings.

Berndt and Hardy described a 4-stage radiographic classification system for the lateral talar dome that is in widespread use and simple, but is limited by the fact that as many as half of OLTs are radiographically occult.

• Stage I: Radiographs are normal. Inversion causes the lateral border of the talar dome to be compressed against the fibula, resulting in a subchondral compression fracture of the talus. The lateral collateral ligament of ankle is intact.
• Stage II: Further inversion ruptures the lateral ligament and begins avulsion of an osteochondral chip. Radiographs show a partially detached osteochondral fragment with a hinge of articular cartilage.
• Stage III: A complete osteochondral fracture with a nondisplaced fragment that remains in the fracture crater.
• Stage IV: A complete osteochondral fracture with a detached fragment.

An MRI classification of the articular cartilage with correlation with arthroscopy has also been developed.

• Grade 0: Normal cartilage.
• Grade I: Abnormal cartilage signal, but morphologically intact cartilage surface.
• Grade II: Fibrillation or fissures not extending to bone.
• Grade III: Chondral flap present or bone exposed.
• Grade IV: Loose undisplaced fragment.
• Grade V: Displaced fragment.

The images above are from a young boy with trauma to the right ankle. We don't have dedicated cartilage imaging at first presentation, so the extent of cartilage injury is unclear. Whatever the signal of the cartilage was at the time, it does appear intact. There is a bone contusion along the anterolateral aspect of the talar dome, which resolved 1 year after the initial MRI. The cartilage overlying the prior area of injury is intact and has normal signal.

References

• Berndt AL, Harty M. Transchondral fractures (osteochondritis dissecans) of the talus. J Bone Joint Surg Am. 1959 Sep;41-A:988-1020. with correction.
• Mintz DN, Tashjian GS, Connell DA, Deland JT, O'Malley M, Potter HG. Osteochondral lesions of the talus: a new magnetic resonance grading system with arthroscopic correlation. Arthroscopy. 2003 Apr;19(4):353-9.
• O'Loughlin PF, Heyworth BE, Kennedy JG. Current concepts in the diagnosis and treatment of osteochondral lesions of the ankle. Am J Sports Med. 2010 Feb;38(2):392-404.

Biopsy of Solid Renal Lesions

The old teaching was that a renal lesion that could not be characterized as either a benign cyst or angiomyolipoma should be surgically resected. This was based the fact that old histologic techniques had high false-negative rates and could not reliably differentiate low-grade renal cell carcinoma from benign oncocytoma. In addition, there was concern for tumor seeding along the biopsy track.

The positive predictive value of biopsy for the diagnosis of renal cell carcinoma is now in the range of 95% – 100%, thanks to new biopsy techniques and histological analyses. In addition, the risk of tumor seeing is now known to be very low. For these reasons, many renal lesions that would have previously been resected, are now biopsied.

Solid renal lesions smaller than about 3 cm are difficult to characterize by imaging; therefore, biopsy may obviate the need for treatment of benign lesions.

Solid renal lesions are also biopsied prior to percutaneous ablation to determine appropriate follow-up and treatment of malignant lesions, and to avoid over-treatment of benign lesions. Indeed, in a series of 27 patients referred for percutaneous ablation, almost 40% of solid renal masses turned out to be benign.

References

• Heilbrun ME, Zagoria RJ, Garvin AJ, Hall MC, Krehbiel K, Southwick A, Clark PE. CT-guided biopsy for the diagnosis of renal tumors before treatment with percutaneous ablation. AJR Am J Roentgenol. 2007 Jun;188(6):1500-5.
• Tuncali K, vanSonnenberg E, Shankar S, Mortele KJ, Cibas ES, Silverman SG. Evaluation of patients referred for percutaneous ablation of renal tumors: importance of a preprocedural diagnosis. AJR Am J Roentgenol. 2004 Sep;183(3):575-82.
• Uppot RN, Harisinghani MG, Gervais DA. Imaging-guided percutaneous renal biopsy: rationale and approach. AJR Am J Roentgenol. 2010 Jun;194(6):1443-9.

CT Halo Sign

The CT halo sign refers to a rim of ground-glass attenuation surrounding a pulmonary nodule or mass. It was first described in invasive pulmonary aspergillosis, and was thought to be specific for that disease. Since the initial description, however, the CT halo sign has been described in a number of other conditions.

• Angioinvasive fungal infection: The most common condition with the CT halo sign in immunocompromised patients. In severely neutropenic patients. Most commonly Aspergillus, but can also be seen with Mucor, Candida, and Coccidioides. Most frequently seen high in the early stages of disease. Ground-glass attenuation halo represents alveolar hemorrhage.
• Bronchoalveolar carcinoma: Mentioned separately because it is the most common condition with the CT halo sign in immunocompetent patients. The tumor can demonstrate lepidic growth, in which tumor cells grow along alveolar walls without destruction of the underlying architecture. Ground-glass attenuation halo represents tumor cell infiltrate.
• Other primary tumors: Squamous cell carcinoma, Kaposi sarcoma.
• Metastases from hypervascular tumors: For example, angiosarcoma, choriocarcinoma, osteosarcoma, melanoma, gastrointestinal malignancies, pulmonary endometriosis (not a neoplasm). Ground-glass attenuation halo represents hemorrhage due to fragility of neovascular tissue.
• Bacterial infection: Mycobacterium (for example, Tuberculosis [ground-glass attenuation halo may represent granulomatous reaction without hemorrhage] and mycobacterium avium complex), Coxiella burnetii.
• Viral infection: Cytomegalovirus, herpes simplex virus, and myxovirus.
• Parasitic infection: Schistosoma.
• Vasculitides: Wegener granulomatosis, for example. Ground-glass attenuation halo represents hemorrhage.
• Septic emboli:
• Trauma: For example, biopsy, lung transplantation.
• Eosinophilic lung disease: Simple eosinophilic pneumonia, hypereosinophilic syndrome.
• Cryptogenic organizing pneumonia: Also see the reversed halo sign in this entity.
• Posttransplantation lymphoproliferative disorder: Ground-glass attenuation halo represents interstitial inflammation mixed with postobstructive endogenous lipoidosis.

References

• Lee YR, Choi YW, Lee KJ, Jeon SC, Park CK, Heo JN. CT halo sign: the spectrum of pulmonary diseases. Br J Radiol. 2005 Sep;78(933):862-5.
• Marten K, Rummeny EJ, Engelke C. The CT halo: a new sign in active pulmonary sarcoidosis. Br J Radiol. 2004 Dec;77(924):1042-5.
• Pinto PS. The CT Halo Sign. Radiology. 2004 Jan;230(1):109-10.

Muscle Knots (Myofascial Trigger Points)

Myofascial trigger points, more commonly known as muscle knots, are stiff, localized spots of exquisite tenderness in a palpable taut band of skeletal muscle. Acute trauma and repetitive microtrauma have been proposed as etiologic factors.

Myofascial trigger points can be classified as active or latent. Active myofascial trigger points are spontaneously painful, tender to palpation, and may be associated with stiffness and restricted range of motion. Latent myofascial trigger points, on the other hand, are not spontaneously painful, but are tender to palpation, and may also be associated with stiffness and restricted range of motion.

Ultrasound findings have been described as ovoid hypoechoic lesions within muscle. Active myofascial trigger points have higher peak systolic velocities and retrograde diastolic flow compared to latent myofascial trigger points on Color Doppler.

References

• Sikdar S, Shah JP, Gebreab T, Yen RH, Gilliams E, Danoff J, Gerber LH. Novel applications of ultrasound technology to visualize and characterize myofascial trigger points and surrounding soft tissue. Arch Phys Med Rehabil. 2009 Nov;90(11):1829-38.

Xanthogranulomatous Pyelonephritis: Bullets

Basics

• Chronic destructive granulomatous process.
• Results from an incomplete immune response to a subacute bacterial infection.
• The renal parenchyma is destroyed and replaced by low-attenuation xanthomatous masses (-10 to 30 HU, depending on the lipid content).
• Calcifications can be seen within these xanthomatous masses (pink arrows).
• Can be focal (10% of cases) or diffuse (90%).
• Focal form can mimic neoplasm.
• Risk factors include diabetes mellitus (10% of patients), female gender (2:1 female:male ratio), and low socioeconomic status.
• Most patients have no specific risk factor.

Imaging:

• Radiography: Large staghorn calculus (nonspecific), enlarged kidney, obscuration of the psoas margin (late finding).
• Intravenous urography: Pronounced decrease in renal function with little or no excretion on delayed imaging (nonspecific).
• Ultrasound: Enlarged kidney with a large shadowing echogenic structure in the renal pelvis (staghorn calculus). Loss of normal renal architecture.
• CT: Combination of the following findings is strongly suggestive of diffuse disease: Nonfunctioning enlarged kidney + staghorn calculus in a contracted renal pelvis + expanded calices (usually filled with a low-attenuation inflammatory exudate) + inflammatory changes in the perinephric fat.
• Focal disease can mimic neoplasm, and should be considered malignant until proven otherwise. Urine culture can be helpful.

The CT images show an enlarged left kidney with multiple low-attenuation parenchymal lesions. One of these in the upper pole has fine calcifications that can be seen on the radiograph (pink arrow). The renal pelvis and the calyces are dilated.

References

• Al-Ghazo MA, Ghalayini IF, Matalka II, Al-Kaisi NS, Khader YS. Xanthogranulomatous pyelonephritis: Analysis of 18 cases. Asian J Surg. 2006 Oct;29(4):257-61.
• Craig WD, Wagner BJ, Travis MD. Pyelonephritis: radiologic-pathologic review. Radiographics. 2008 Jan-Feb;28(1):255-77.
• Fan CM, Whitman GJ, Chew FS. Xanthogranulomatous pyelonephritis. AJR Am J Roentgenol. 1995 Oct;165(4):1008.

Adrenal Cortical Carcinoma

Adrenal cortical carcinoma (also known as adrenocortical carcinoma) is a malignant neoplasm that originates from the adrenal cortex. It is rare, with an estimated incidence of 1–2 per million population.

There is a bimodal age distribution, with increased incidence in children younger than 5 years of age and in adults in their 30s and 40s. Adrenal cortical carcinomas are more common in women, in whom the tumors tend to be well-differentiated and functional. The tumors are also more likely to be functional in children (>85%) compared to adults (< 30%). Functional tumors can secrete cortisol (Cushing syndrome), androgens (virilization), estrogens (feminization), and/or aldosterone (Conn syndrome). The "and/or" in the previous sentence is meant to indicate that unlike benign adrenal cortical tumors, which tend to secrete a single class of steroid, adrenal cortical carcinomas can secrete various types of steroids. Indeed, rapidly progressing Cushing syndrome, often with virilization, is a characteristic presentation in adults.

Unfortunately, most tumors in adults are non-functional, and patients typically present late with mass effect from a large tumor, with 30% of patients presenting with metastatic disease.

Most cases are sporadic; however, adrenal cortical carcinomas have been associated with Li-Fraumeni syndrome, Carney complex (not to be confused with the Carney triad), Beckwith-Wiedemann syndrome, familial adenomatous polyposis, and multiple endocrine neoplasia, type 1.

Imaging findings at CT include a large (> 4 cm) hemorrhagic and necrotic mass with small areas of fat (from cortisol and its fatty precursors in functional tumors) and calcification (seen in ~30% of patients.

Smaller lesions may be homogeneous on unenhanced CT, but demonstrate heterogeneous enhancement and central low attenuation from necrosis.

MRI findings include a heterogeneous mass with areas of T1 hyperintensity corresponding to hemorrhage. The lesions are predominantly T2-hyperintense. Foci of intracellular lipid corresponding to cortisol and its fatty precursors can be demonstrated as non-uniform areas of signal loss on chemical shift imaging.

References

Bharwani N, Rockall AG, Sahdev A, Gueorguiev M, Drake W, Grossman AB, Reznek RH. Adrenocortical carcinoma: the range of appearances on CT and MRI. AJR Am J Roentgenol. 2011 Jun;196(6):W706-14.

Hemangioma of the Long Bones

We're all familiar with the appearance of osseous hemangiomas of the vertebral bodies -- osseous hemangioma is common in the axial skeleton, with 75% occurring in the spine and calvaria. Twenty percent of cases occur in the scapula, ribs, clavicle, and pelvic bones, and involvement of the long bones is rare. Osseous hemangiomas occur in young adults, with a mean age of ~30 years, and are more common in women. The majority (90%) of patients are symptomatic. 10% of patients present with a pathological fracture.

In the long bones, osseous hemangiomas can be classified as medullary (~50%), periosteal (~35%), and intracortical (~15%).

Medullary osseous hemangiomas occur most commonly in the diaphysis (48% of cases), with metadiaphyseal (30%), metaphyseal (12%), metaepiphyseal (4%), epimetadiaphyseal (3%) and epiphyseal (1%) lesions occurring less commonly. On radiographs, medullary lesions can have corduroy and radiating trabecular thickening similar to those seen in the vertebral bodies and skull, respectively, but this is an uncommon presentation. A more common appearance is a bubbly pattern of bone lysis that creates a honeycomb, lattice-like, or "hole-within-hole" appearance. This bone lysis can appear as linear and circular densities on radiographs, representing vascular channels seen longitudinally and en face, respectively. The appearance can mimic that of lymphoma, osteomyelitis and metastatic disease.

On CT, medullary hemangiomas appear as expansile lytic areas surrounded by coarse trabecular bone. A "polka dot" appearance, when seen, can suggest the diagnosis.

On MRI, the vascular channels are hypointense on T1-weighted images and hypointense to very hyperintense on T2-weighted images depending on the speed of blood flow. The trabeculations may be seen as areas of low signal.

Less common radiographic appearances include punched-out lucencies that can mimic metastatic disease or multiple myeloma; large, lytic, lesions with sclerotic borders that can mimic giant cell tumor, unicameral or aneurysmal bone cyst, or fibrous dysplasia; and permeative pattern that can mimic multiple myeloma, metastatic carcinoma, lymphoma, or Ewing sarcoma. In these cases, the rarity of osseous hemangioma would preclude its inclusion in the differential diagnosis.

Periosteal and intracortical lesions also occur most commonly in the diaphyis (~75%), wit the anterior tibial diaphysis being a common location. Metadiaphyseal (~15%) and metaphyseal (~10%) lesions can also be seen. On radiographs, they present as small, well-defined lytic lesions that may also be associated with cortical thickening and/or periosteal reaction. The differential diagnosis includes stress fracture, osteoid osteoma, or cortical abscess.

On MRI, intracortical lesions appear as increased signal within the normally dark cortex.
Should be considered in the differential diagnosis of fat-containing bone lesions.

References

• Chawla A, Singrakhia M, Maheshwari M, Modi N, Parmar H. Intraosseous haemangioma of the proximal femur: imaging findings. Br J Radiol. 2006 Aug;79(944):e64-6.
• Greenspan A, Jundt G, Remagen W. Vascular Lesions. In Differential Diagnosis of Orthopaedic Oncology, 2nd Edition. 2007 Lippincott Williams & Wilkins; pp 366-367.
• Kaleem Z, Kyriakos M, Totty WG. Solitary skeletal hemangioma of the extremities. Skeletal Radiol. 2000 Sep;29(9):502-13.
• Levine SM, Lambiase RE, Petchprapa CN. Cortical lesions of the tibia: characteristic appearances at conventional radiography. Radiographics. 2003 Jan-Feb;23(1):157-77.
• Murphey MD, Fairbairn KJ, Parman LM, Baxter KG, Parsa MB, Smith WS. From the archives of the AFIP. Musculoskeletal angiomatous lesions: radiologic-pathologic correlation. Radiographics. 1995 Jul;15(4):893-917.

Benign Fibrous Histiocytoma of Bone

Benign fibrous histiocytoma of bone (also known as fibroxanthoma, fibrous xanthoma, xanthofibroma, and xanthogranuloma) is a rare benign lesion that is histologically indistinguishable from non-ossifying fibroma, but with location and clinical or radiographic presentation atypical for non-ossifying fibroma.

In contrast to non-ossifying fibroma, patients are often older, with 60% older than 20 years of age. Patients are also often symptomatic (85% of cases) and present with pain in 65% of cases. The location is also atypical for non-ossifying fibroma, with epiphyseal and diaphyseal localization being common in the long bones. The lesions can also occur in the pelvic bones in 25% of cases (virtually any bone can be involved). Also in contrast to non-ossifying fibroma, benign fibrous histiocytoma of bone can be locally aggressive and recur after curettage or excision.

Radiographic findings can be similar to non-ossifying fibroma, including a well-defined, radiolucent lesion with a sclerotic border. The sclerotic border can be absent in 1/3 of cases. Internal trabeculation or pseudoseptation can be present in some cases. The lesion can either be medullary (more common in general) or eccentric (more common with epiphyseal lesions). More aggressive features, such as endosteal thinning and bone expansion, can be seen. A periosteal reaction is usually not seen in the absence of superimposed pathologic fracture.

MRI findings include intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Differential considerations include:

• Non-ossifying fibroma: May be indistinguishable from benign fibrous histiocytoma
• Giant cell tumor: Rarely has a rim of reactive sclerosis, which is common in benign fibrous histiocytoma. Some consider benign fibrous histiocytoma a burned-out giant cell tumor.
• Intraosseous ganglion: Usually smaller than benign fibrous histiocytoma of bone, but may be considered in cases of epiphyseal lesions.
• Chondromyxoid fibroma:
• Osteoblastoma: Usually has a periosteal reaction and looks like osteoid osteoma, but can also appear as an expansile lucency with a sclerotic rim and internal calcifications. The internal calcifications can simulate a chondroid matrix and can help differentiate this presentation of osteoblastoma from benign fibrous histiocytoma of bone.

benign fibrous histiocytoma of bone should be distinguished from benign fibrous histiocytoma of soft tissues.

References

• Greenspan A, Jundt G, Remagen W. Fibrogenic, Fibroosseous, and Fibrohistiocytic Lesions. In Differential Diagnosis of Orthopaedic Oncology, 2nd Edition. 2007 Lippincott Williams & Wilkins; pp 266-267.
• Kyriakos M. Benign fibrous histiocytoma of bone. In World Health Organization Classification of Tumours: Pathology and Genetics of Tumours of Soft Tissue and Bone. Fletcher CDM, Unni KK, Mertens F (eds). IARCPress Lyon, 2002. pp 292-293.

Fossae at the Bases of Metatarsals

Normal fossae can be seen at the bases of the metatarsals and should not be confused with erosions or fractures.

References

Keats TE and Anderson MW. Atlas of Normal Roentgen Variants That May Simulate Disease - 8th edition (Mosby, 2004), p 942.

Ovarian Neoplasms with Calcifications

• Serous carcinoma (shown above): Often exhibit papillary histology, which is associated with psammoma calcification. The calcification is typically punctate, but can be amorphous.
• Fibrothecoma: Dense calcifications are often seen.
• Teratoma: Calcifications in mature teratomas (dermoid cysts) are localized to mural nodules, while those of immature teratomas have a more scattered distribution.
• Brenner tumor: Can have extensive amorphous calcification within the solid component
• Dysgerminoma: The ovarian counterpart to the seminoma. Can contain calcifications in a speckled pattern.

References

• Burkill GJ, Allen SD, A'hern RP, Gore ME, King DM. Significance of tumour calcification in ovarian carcinoma. Br J Radiol. 2009 Aug;82(980):640-4.
• Jung SE, Lee JM, Rha SE, Byun JY, Jung JI, Hahn ST. CT and MR imaging of ovarian tumors with emphasis on differential diagnosis. Radiographics. 2002 Nov-Dec;22(6):1305-25.
• Moon WJ, Koh BH, Kim SK, Kim YS, Rhim HC, Cho OK, Hahm CK, Byun JY, Cho KS, Kim SH. Brenner tumor of the ovary: CT and MR findings. J Comput Assist Tomogr. 2000 Jan-Feb;24(1):72-6.

Myofibroblastoma

Myofibroblastoma, also known as myogenic stromal tumor, is a rare benign tumor of the breast characterized histologically by spindle cells (myofibroblasts) in fascicles with varying degrees of myogenic and fibroblastic differentiation. Initially felt to be a tumor predominantly of the male breast, more recent studies have shown that the sex distribution may not be as skewed towards males.

Mammographic findings sometimes suggest a benign diagnosis: A circumscribed lesion without architectural distortion. Coarse calcifications have been reported in association with myofibroblastomas. A case of myofibroblastoma mimicking a hamartoma has been described at our institution, and a case of myofibroblastoma arising in a hamartoma has also been reported in the pathology literature.

However, the tumor may also be mammographically occult or have ill-defined margins.

Ultrasound reveals a circumscribed hypoechoic to mildly hyperechoic lesion with or without distal acoustic attenuation.

References

• Greenberg JS, Kaplan SS, Grady C. Myofibroblastoma of the breast in women: imaging appearances. AJR Am J Roentgenol. 1998 Jul;171(1):71-2.
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