Metastatic Disease to the Breast

Metastatic disease to the breast is uncommon and represents less than 2% of all breast malignancies. Sources of metastases include carcinoma of the opposite breast, lymphoma, leukemia, and melanoma. In children, rhabdomyosarcoma is the most common cause while in males prostatic adenocarcinoma is the most common culprit.

Metastases to the breast differ from primary breast carcinoma in that chest wall fixation, skin/nipple retraction, spiculations, and microcalcifications are generally not seen. Metastases are more like to be multiple and bilateral than primary malignancies.

There are two mechanisms of occurrence of metastases to the breast: lymphangitic and hematogenous spread. The former occurs across the anterior thoracic wall with the contralateral breast as the source. This gives an appearance of dense subcutaneous fat with thickened trabecular pattern. As the tumor spreads via lymphatics, the glandular stroma of the breast also appears dense and irregular. This appearance is indistinguishable from that of inflammatory breast carcinoma and is most commonly seen with metastases from the contralateral breast and gastric carcinoma. A solitary discrete lesion is the most common appearance of hematogenous metastases to the breast.


REFERENCES

Feder JM, De Paredes ES, Hogge JP, et al. Unusual breast lesions: radiologic-pathologic correlation. Radiographics. 1999 October;19:S11-S26.
Lee SH, Park JM, Kook SH, et al. Metastatic tumors to the breast: mammographic and ultrasonographic findings. J Ultrasound Med. 2000;19:257-62.

Mercury Emoblism to the Lung

Nonthrombotic pulmonary emboli are rare and the imaging findings are specific to the origin of the embolus. Types of nonthrombotic emboli include septic emboli, fat emboli, amniotic fluid emboli, and air emboli. Iodinated oil emboli have been reported after transcatheter chemoembolization of hepatocellular carcinoma. Substances such as talc used in preparation of amphetamines by drug addicts can also embolize to the pulmonary arterial tree.

The above image is from a patient who attempted suicide via intravenous mercury injection. The xray image shows multiple metallic spherules throughout both lungs which is the typical imaging appearance for mercury emboli.


REFERENCES
Han D, Lee KS, Franquet T, et al. Thrombotic and nonthrombotic pulmonary arterial embolism: spectrum of imaging findings. Radiographics. 2003 November;23:1521-39.
Rossi SE, Goodman PC, Franquet T. Nonthrombotic pulmonary emboli. AJR Am J Roentgenol 2000;174:1499-1508.

Idiopathic Dilatation of the Pulmonary Artery

Aneurysms of the main pulmonary artery are rare. About half are attributed to congenital heart disease and are usually associated with pulmonary hypertension. Acquired causes include infection (syphilis, tuberculosis, bacterial endocarditis), vasculitis (Behcet's and Hughes-Stovin syndromes), connective tissue abnormalities (Ehlers Danlos, Marfan's, cystic medial necrosis), and trauma (including malpositioned Swan-Ganz catheters causing iatrogenic pulmonary artery pseudoaneurysm). The aforementioned causes need to be excluded before idiopathic dilatation of the pulmonary artery is considered.

CECT parameters for a normal pulmonary artery are:

1. transverse diameter of main pulmonary artery < 28-29 mm, measured at the bifurcation, perpendicular to the long axis of the artery,
2. main pulmonary artery with a smaller diameter than the adjacent aorta,
3. transverse diameter of right interlobar artery < 16 mm.

Focal dilatation of the pulmonary artery exceeds these parameters. In addition to a dilated main pulmonary artery, CECT may also show enlargement of the right and left pulmonary arteries.


REFERENCES

Nair KKS and Cobanoglu AM. Idiopathic main pulmonary artery aneurysm. Ann Thorac Surg 2001;71:1688-90.
Nguyen ET, Silva CIS, Seely JM, et al. Pulmonary artery aneurysms and pseudoaneurysms in adults: findings at CT and radiography. AJR Am J Roentgenol 2007;188:W126-W134.
Ring NJ and Marshall AJ. Idiopathic dilatation of the pulmonary artery. Brit J Radiol 2002;75:532-5.

Significance of Intraperitoneal Free Fluid in Male Trauma Patients Without Identifiable Injuries

MDCT is routinely used in the evaluation of blunt abdominal trauma. The presence of intraperitoneal free fluid in the absence of identifiable injury presents a diagnostic challenge, especially in male patients (in female patients, free fluid, especially when seen in the pouch of Douglas, can be a normal physiologic finding).

In the late 1990s the presence of free fluid without identifiable injury necessitated exploratory laparotomy. Since then, studies have advocated for conservative management such as admitting the patient for observation rather than proceeding with surgical intervention.

In their study of 669 consecutive male trauma patients, Drasin and Anderson show that approximately 3% of patients can have the finding of isolated free fluid without clinical significance They advocate for the evaluation of factors such as size and attenuation measurements of fluid when triaging the patient and suggest that observation with repeat imaging may prevent unnecessary laparotomies. 


REFERENCES

Drasin TE, Anderson SW, Asandra A, et al. MDCT evaluation of blunt abdominal trauma: clinical significance of free intraperitoneal fluid in males with absence of identifiable injury. AJR Am J Roentgenol 2008;191:1821-26.
Levin CD, Patel UJ, Wachsberg RH, et al. CT in patients with blunt abdominal trauma: clinical significance of intraperitoneal free fluid detected on a scan with otherwise normal findings. AJR Am J Roentgenol 1995;164:1381-85.

The Target Sign: Bowel vs Bone

The target sign is a well known entity in abdominal imaging. It refers to the CECT stratified appearance of bowel wall layers in the setting of inflammation. Specifically, there is high attenuation of the inner and outer layers of the bowel representing hyperemia of the mucosa and muscularis propria. The low attenuation of the submucosa is believed to be secondary to edema. This appearance is best seen when imaging is performed during the late arterial/early venous phase. The intensity of bowel wall enhancement is felt to correlate with the severity of disease. 

The target sign is a nonspecific finding as it can be seen several entities including inflammatory bowel disease, ischemic colitis, and radiation induced colitis. While the most common CECT finding in bowel inflammation is bowel wall thickening, the presence of a target sign can lead towards the diagnosis of a benign entity since the sign is uncommon in malignancy (the exception being the occurrence of the target sign in cases of infiltrating scirrhous carcinoma of the rectum).

A less well known usage of the target sign is in reference to the appearance of peripheral nerve sheath tumors (PNSTs) on axial T2 weighted MR images where a central area of low signal intensity is surrounded by an area of high signal intensity. In this context, the target sign appearance is due to the histologic composition of the tumor: the central low signal is due to the fibrocollagen tissue in the lesion's core, while the peripheral high signal is due to the presence of myxomatous tissue.

PNSTs are classified as benign (neurofibroma, schwannoma) and malignant (neurofibrosarcoma, malignant schwannoma). The clinical distinction between benign and malignant entities is difficult due to significant overlap in their manifestation. The target sign is most commonly seen in neurofibromas which tend to have a separation of cellular and noncellular component. It is thought that when the target sign is seen in regions of a malignant PNST, the areas demonstrating the sign represent benign tissue while the areas without the target sign represent tissue that has undergone malignant transformation.


REFERENCES

Ahualli J. The target sign: bowel wall. Radiology. 2005 February;234:549-50.
Banks KP. The target sign: extremity. Radiology. 2005 March;234:899-900.

Phthisis Bulbi

Phthisis bulbi refers to an atrophic, disorganized globe with calcifications. It is an end-stage ocular condition that can be a sequela of ocular inflammation, trauma, radiation, infection, and retinal detachment. The effected eye is non-functioning. 

The above images demonstrate a shrunken, calcified left globe in a patient with confirmed phthisis bulbi. The patient has had scleral banding on the right.


REFERENCES

LeBedis CA and Sakai O. Nontraumatic orbital conditions: diagnosis with CT and MR imaging in the emergent setting. Radiographics. 2008 October;28:1741-53.
Mafee MF. The eye. In: Som PM, Curtis HD, eds. Head and neck imaging. 4th ed. St. Louis, MO: Mosby, 2003; 441-527.

Spontaneous Intramural Small-Bowel Hematoma

Spontaneous intramural hematoma of the small bowel is most often attributed to over-anticoagulation with warfarin. Other causes include bleeding disorders, malignancy, vasculidities, and trauma. Typically, the duodenum and jejunum are involved. 

The hemorrhage is usually in the submucosal layer of the small bowel. Intraluminal, intramesenteric, and retroperitoneal extension can occur. Hemorrhagic ascites may be present.

The CT appearance depends on the age of the hematoma. Initially, thickened small bowel loops with intramural hyperdensity will be seen. As the clot lyses, the attenuation decreases and the thickened bowel wall appears hypodense.

Treatment consists of normalizing the INR with bowel resection reserved for cases presenting with high grade bowel obstruction. Follow up imaging will demonstrate a resolution of CT findings within a few weeks.

The above clip is from a patient with a history of atrial fibrillation on warfarin who presented with a 5 day history of vague abdominal pain and was found to have a supratherapeutic INR. CECT demonstrated hemorrhagic ascites with thickened, hyperdense loops of jejunum.

REFERENCES

Abbas MA, Collins JM, Olden KW. Spontaneous intramural small-bowel hematoma: imaging findings and outcomes. AJR Am J Roentgenol. 2002 Dec;179(6):1389-94.
Boudiaf M, Soyer P, Terem C, et al. CT evaluation of small bowel obstruction. Radiographics. 2001 May;21:613-24.