Sunday, March 12, 2017

Fat-containing bone lesions


The presence of fat within a bone lesion is almost always reassuring, although rare exceptions exist. The differential diagnosis includes:
  • Hemangioma:
  • Intra-osseous lipoma and lipoma variants, including fibrolipoma, angiolipoma and myelolipoma.
  • Enchondroma:
  • Liposclerosing myxofibrous tumor (LSMFT): Nearly all occur in the intertrochanteric region. Now felt to represent a variant of fibrous dysplasia.
  • Osteoporosis: Can give the appearance of lucent bone lesions on CT. These won't have defined margins, and measurement of internal attenuation will reveal the fatty nature of the lesion.
  • Bone infarction: Trivial, but included for the sake of completeness
  • Paget disease of bone:
  • Focal red marrow rest: Ill-defined, intermediate T1 signal. May contain subtle areas of internal fat.
  • Lymphoma: Not truly a fat-containing lesion, but can entrap fat as the tumor infiltrates marrow.
  • Sarcoid: The case above shows a patient with sarcoid and nodal, hepatic, and osseous involvement. Can have fuzzy margins ("brush border").
  • Treated metastasis: One of the ways metastases respond to therapy is by developing internal fat. Myeloma lesions can even entirely "disappear" due to fatty replacement.
  • Intra-osseous hibernoma: Rare.
  • Solid variant of aneurysmal bone cyst:
  • Nonossifying fibroma:
  • Erdheim-Chester disease:
  • Malignancy arising from a fat-containing lesion: For example, osteosarcoma arising from bone infarction or Paget.

References

Sunday, March 5, 2017

Subperiosteal hemorrhage in neurofibromatosis type 1



Neurofibromatosis type 1 (NF-1), in addition to a neuroectodermal disorder, is accompanied by mesodermal dysplasia that is accompanied by skeletal changes. The typical osseous findings include bowing of the legs, increase in length of long bones, pseudarthrosis, subperiosteal cyst formation, local bony erosions from adjacent lesions, and intramedullary neurofibromas. Except for the last two, which are due to direct involvement by neurofibromas, the remainder are due to dysplastic changes in bones.

A lesser known osseous presentation in bone is the propensity for subperiosteal hemorrhage and hematoma formation. The cause is unknown, but may be related to:
  • Vascular abnormalities: For example, diffuse flat hemangiomas or plexiform dilated veins, which have been described in patients with hypertrophy of the extremities
  • Dysplastic periosteum: The thinking is that mesodermal dysplasia manifests as an abnormally loose periosteum with poor callus response. This would predispose the patient to the formation and propagation of large subperiosteal hematomas.
  • Direct involvement by neurofibromas: Subperiosteal infiltration by neurofibromatous tissues may loosen the periosteum and allow for massive hemorrhage following minor trauma.

References

Sunday, February 26, 2017

The Lamina Dura



The lamina dura is the bony lining of the socket (alveolus) of a tooth. The periodontal ligaments extend from the lamina dura to the cementum of the tooth, an keep the tooth in place. The lamina dura is cribriform plate produced by the periodontal ligament and fibers of the periodontal ligament are embedded within it.

While loss of the lamina dura (arrow in image above) is sometimes said to be pathognomonic for hyperparathyroidism, it can be seen in a wide range of conditions:
  • Hyperparathyroidism: The case above is from a patient with primary hyperparathyroidism.
  • Osteomalacia
  • Osteoporosis
  • Paget disease
  • Leukemia
  • Myelomatosis
  • Cushing disease


The lamina dura can be thickened in bisphosphonate-related osteonecrosis of jaw (BRONJ)

References

Sunday, February 19, 2017

Systemic Mastocytosis


Systemic mastocytosis (SM) refers to mast cell infiltration in extra-cutaneous tissues. The symptoms of systemic mastocytosis are due to degranulation of mast cells and/or accumulation of mast cells in target organs.

Degranulation of mast cells

Symptoms can be caused by secretion of the following factors:
  • Histamine: Pruritus, urticaria, hypotension, gastric hypersecretion, bronchoconstriction.
  • Heparin: Local anticoagulation, osteoporosis
  • Leukotrienes: Bronchoconstriction
  • Prostaglandins: Bronchoconstriction, flushing
  • Platelet-activating factor:
  • Proteases:
  • Tumor necrosis factor:

Accumulation of mast cells in organs

Accumulation of mast cells in organs can cause organ dysfunction. The so-called B findings refer to organ involvement without organ dysfunction. C findings refer organ involvement with organ dysfunction. The example above shows hepatic involvement with cirrhosis (white arrow) and ascites (yellow arrow) and nodal involvement with bulky adenopathy (red arrow). We also have involvement with diffuse sclerosis. Interestingly, the non-radiology literature stresses the more common osteoporosis, with scarce mention of the sclerosis that tends to dominate the radiology literature.

Diagnosis systemic mastocytosis

The diagnosis of SM requires either, 1 major and 1 minor OR 3 minor criteria. Warning: Boring for radiologists

The one major criterion is: Multifocal, dense infiltrates of mast cells (≥15 mast cells in aggregates) in sections of bone marrow and/or other extra-cutaneous organ(s).

Minor criteria are:
  • Bone marrow or other extra-cutaneous organs: >25% of mast cells in the infiltrate are spindle-shaped or have atypical morphology, or of all mast cells in bone marrow aspirate smears, >25% are immature or atypical.
  • Activating point mutation at codon 816 of KIT in bone marrow, blood, or another extra-cutaneous organ.
  • Mast cells in bone marrow, blood, or other extracutaneous organs express CD2 and/or CD25 in addition to normal mast cell markers.
  • Serum total tryptase persistently > 20 mg/mL (unless associated w clonal myeloid disorder).

Subtypes

  • Indolent (ISM): No C findings
  • Smoldering (SSM): 2+ B findings, no C findings
  • Aggressive (ASM): C findings, no MCL features*
  • Mast cell leukemia (MCL): BMBx diffuse infiltration by atypical, immature mast cells. Aspirate smears ≥20% mast cells.
  • SM with associated hematologic neoplasm (SM-AHN): SM + MDS, MPN, AML, lymphoma, other

References

Akin C, Gotlib J. Systemic mastocytosis: Determining the subtype of disease. UpToDate

Sunday, February 12, 2017

The Cervical Split: A Pseudofracture


A horizontal line projecting over a cervical vertebral body on lateral radiographs can simulate a fracture or a butterfly vertebral body. This pseudofracture, the so-called cervical split, can result from the lucency between contiguous uncovertebral osteophytes, or, as in the case above, cervical scoliosis resulting in projection of the facet joint over the vertebral body.

A cervical split due to uncovertebral joint osteophyte formation is said to be always accompanied by disc space narrowing.

References

Thursday, February 2, 2017

Chronic Subperiosteal Iliac Hematoma



Subperiosteal iliac hematoma is caused by traumatic avulsion of the periosteum in children and young adults. The loose attachment of periosteum in young patients allows it to be displaced by hematoma in trauma. In the chronic phase, it is typically incidentally discovered by radiologists.

In the chronic phase, it presents as a lens-shaped ossified process on the internal aspect of the iliac wing with a ghost cortex (dotted line in the image above). It may or may not have the well-defined central lesion we have in this case.

References

Guillin R, Moser T, Koob M, Khoury V, Chapuis M, Ropars M, Cardinal E. Subperiosteal hematoma of the iliac bone: imaging features of acute and chronic stages with emphasis on pathophysiology. Skeletal Radiol. 2012 Jun;41(6):667-75.

Wednesday, December 21, 2016

M.D. = Makes Decisions (unless you're a radiologist)

#
1 This is a cat. This is a hemangioma.
2 This is most likely a cat. This is most likely a hemangioma
3 This is consistent with a cat. This is consistent with a hemangioma.
4 This is most likely a cat, but get a follow-up picture to make sure it wasn't a baby tiger all along. This is most likely a hemangioma. Recommend follow-up to document stability.
5 This is most likely consistent with a cat. This is most likely consistent with a hemangioma.
6 This is likely a cat, but can't exclude a tiger hiding behind it way in the distance. This is likely a hemangioma, but can't exclude malignancy, sarcoid, etc.
7 This is likely a cat. Why don't you take a look for yourself and stop bothering me? This is likely a hemangioma. Recommend clinical correlation.
8 This is likely a cat, but get a saliva sample and send it in for genetic analysis. Better yet, kill the cat and dissect it. This is likely a hemangioma. Recommend biopsy. Open biopsy may be required.


In the real world (with the cat), anything other than statement #1 will get you laughed at. In radiology, statement #1 is rare. Instead we teach our residents and fellows, by our own weak examples, to be as non-declarative as possible.

Statements #2 and #3 are as declarative as most radiologists get. "I said most likely. What more do you want from me?!"

Statement #4 just passes the buck to the next radiologist.

Statement #5 combines 2 mild hedge words to produce one super-hedgy sentence.

Statement #6 is the reason Bayes rolls in his grave every time a radiologist signs a report.

Statement #7 is basically saying, "Thanks for the money suckers! This report was useless." We have access to so much patient data these days that it baffles me to see this in reports. Of course, this doesn't apply to cases where we're reading in isolation and when the only history we get from referrings is "pain," or some random ICD code. This negligent absence of data in a requisition borders on (is?) malpractice. I've seen it in imaging referrals my family members get from their doctors and it aggravates me to no end.

Statement #8, I don't even... For a cat/hemangioma?

Look, sometimes we have to hedge. Sometimes we are no better than Plato's cave captives, squinting at shadows with no idea of what's behind us. We know that two or more widely disparate entities can have identical imaging features. But when you know something can only be one thing, just say so. Save the patient some anxiety. And, save the rest of us some money by reducing unnecessary imaging.

What are some of your favorite radiology hedges?