Case for diagnosis. Atypical fibroxanthoma.

Atypical fibroxanthoma is a rare cutaneous tumor found mainly in elderly people on sun-exposed areas of the body. Histologically, atypical fibroxanthoma is considered a malignant fibrous histiocytoma with bizarre neoplastic cells, marked pleomorphism, hyperchromatic nuclei and abundant mitoses. It must be differentiated from other skin tumors, usually by immunohistochemistry, since its diagnosis is made by exclusion.