Track: Case Reports

Abstract:

Atypical fibroxanthoma is a neoplasm of uncertain histogenesis that typically arises on sun-damaged skin of elderly patients. Histopathologically, the tumor is circumscribed, based in the dermis and consists of pleomorphic spindle to epithelioid cells without necrosis. Multiple subtypes including clear cell, sclerotic, keloidal, myxoid and granular cell atypical fibroxanthomas have been described. Atypical fibroxanthoma with granular cell change is exceptionally rare, and only small case reports about this subtype exist. We present two atypical fibroxanthomas with granular cell change affecting the scalp of a 76-year-old and the forearm of a 67-year-old man. Both showed dermally based sheets and fascicles composed of epithelioid and spindle cells with marked nuclear pleomorphism, abundant granular cytoplasm and a maximum of 5 mitoses per high ten power fields. No necrosis was present. By immunohistochemistry, the cells were negative for S100, SOX10, AE1/AE3, CD34, SMA, desmin, ALK and NTRK, but positive for CD10 and CD68. In summary, atypical fibroxanthoma with granular cell change poses a diagnostic challenge due to benign mimickers such as granular cell tumor and non-neural granular cell tumor. Conventional granular cell tumor is distinguished by positivity for S100 and SOX10. Non-neural granular cell tumor can be distinguished by ALK positivity in most cases.

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Sean Stephenson