Fat necrosis mimicking malignancy in a man with gynaecomastia

Clinical History

The patient presented with bilateral breast swelling, with a more defined and indurated retroareolar mass in the left breast, measuring about 4 cm. He had a history of alcoholism with liver cirrhosis and recent falls. Three months before he was submitted to a liver transplant for a stage II hepatocellular carcinoma.

Imaging Findings

The palpable mass corresponded to a flame-shaped subareolar density with deep linear extensions (Fig. 1b, d), indicating long-standing gynaecomastia due to previous liver cirrhosis. The right breast had similar findings (Fig. 1a, c).

In the left breast, there was also a spiculated dense oval mass with no associated calcifications (Fig. 1b, d). Sonographically, it corresponded to a 10 mm oval heterogeneous hypoechoic mass, with spiculated borders and no posterior acoustic features (Fig. 2). This mass was located in the upper outer quadrant, in a deep retroareolar position, 12 mm from the nipple and from the skin surface, not readily palpable.
Categorized as BI-RADS 4C, the recommended ultrasound-guided biopsy revealed the diagnosis of fat necrosis, probably secondary to trauma.

In a CT examination performed a year later for an infectious disease, gross calcifications were noticed in the spiculated mass (Fig. 3), concordant with the diagnosis. A non-recent rib fracture and a moderate left pleural effusion with signs of loculation were also seen.

Discussion

Radiologists are generally less acquainted with male breast disease. [1]
Gynaecomastia is a benign proliferation of ducts and supporting tissue and the most frequent male breast disease [2, 3], responsible for 85% of male breast masses. [4] It has many causes including cirrhosis, neoplasms, senescence, drugs and hypogonadism. [2, 4] While symptoms (pain, breast mass) may be unilateral, imaging findings are generally bilateral and asymmetric. [5, 6]
There are three radiological patterns (nodular, dendritic and diffuse) that correlate with the clinical and pathologic findings. [2, 5] A flame-shaped subareolar density with deep linear extensions represents the dendritic pattern of long-standing irreversible gynaecomastia. [3, 5, 6] The abnormalities are usually hypoechoic at ultrasound, but there can be increasing hyperechogenicity with the development of fibrosis. [1, 3, 4]
Gynaecomastia can be reversed if the cause is corrected before progression to fibrosis. [7]

Fat necrosis, on the other hand, is very rare in the male breast.[8] There are multiple aetiologies, which, when present in the clinical history, may suggest the diagnosis. [9, 10] These include blunt trauma, previous breast procedures, radiotherapy and anticoagulant use.[9, 11, 12] They cause local destruction of fat, leading to inflammation and subsequent fibrosis. [4]
Frequently asymptomatic [9], fat necrosis can mimic breast cancer, both clinically and radiologically. [4, 11]
The radiological findings are influenced by the histologic stage. [8, 9]
When there is minimal fibrosis, oil cysts are a common mammographic finding. [13] These radiolucent round masses are a pathognomonic feature, representing cystic areas of necrotic fat. [7, 10]
When fibrosis predominates, a dense mass is observed. [13] However, only 4% of cases present with a spiculated mass. [9] Distortion and skin retraction are also possible findings. [4, 9]
Calcifications are frequently seen and sometimes are the only finding. [9, 11, 13] Eggshell calcifications of oil cysts are typical features [4, 9], but suspicious microcalcifications may also be present. [3, 4]
At ultrasound, fat necrosis may correspond to a solid, complex or anechoic mass [7, 8, 13], with circumscribed or non-circumscribed margins. [11, 13] There can be posterior acoustic enhancement or attenuation. [8, 11]
Typical MRI signs are isointensity to fat, thin rim of enhancement and peripheral location. [9, 12] However, haemorrhagic and inflammatory components can decrease the T1 signal intensity and fibrotic lesions are more spiculated, increasing the suspicion of malignancy. [10, 12, 13]
Occasionally fat necrosis is detected on CT, due to the low attenuation of fat. [10] Calcifications are evident in later stages. [10]
When diagnosis cannot be established by imaging, biopsy should be pursued. [12]
At follow up, most lesions decrease in size and/or develop dystrophic calcifications. [9]

Differential Diagnosis List

Final Diagnosis

Fat necrosis of the breast

URL:	https://www.eurorad.org/case/12852
DOI:	10.1594/EURORAD/CASE.12852
ISSN:	1563-4086