Abstract

Cutaneous post-radiation angiosarcoma can clinically and histologically mimic benign vascular entities, leading to misdiagnosis. We present five women, status-post radiation for breast cancer, who were diagnosed with the rare capillary lobule pattern of post-radiation angiosarcoma. The patients had a mean age of 76-years (range 55-96 years). Available clinical history was limited, as these were consultations. Sections demonstrated a prominent lobular/nodular pattern of closely packed vessels lined by enlarged hyperchromatic endothelial cells. Multilayering was seen in the lobules in 1 of 5 cases. In the background, there were also infiltrating cord-like vessels (5/5) and atypical single endothelial cells (5/5). The neoplastic cells were positive for CD31 (4/4), CD34 (2/2) ERG (1/1) and c-MYC (4/4). SMA highlighted pericytes in capillary lobules in 4 of 4 cases, in conventional angiosarcoma areas in 1 of 2 cases, and in individual vascular channels in 2 of 4 cases. MYC amplification by FISH was confirmed in 2 of 2 cases. The capillary lobule pattern of post-radiation angiosarcoma is rare, with only four previously reported cases. Given its lobular architecture, it may mimic entities such as a lobular capillary hemangioma or tufted angioma. The presence of SMA-positive pericytes in the lobules has not been previously reported and is a potential diagnostic pitfall, as conventional angiosarcoma typically lacks this feature. Careful attention to histopathologic features, recognition of background features of more conventional angiosarcoma, and demonstration of c-MYC expression or MYC amplification should allow recognition. It is critical for dermatopathologist to be aware of this pattern to avoid potential misdiagnosis.

Financial Disclosure: No current or relevant financial relationships exist.