Clear cell atypical fibroxanthoma: a case report and review of the literature.

Atypical fibroxanthoma (AFX) is a group of cutaneous tumors characterized by a population of fusiform, epithelioid and pleomorphic cells. Clinically, AFX is commonly found on the head and neck of older adults as a solitary ulcerated nodule. Clear cell atypical fibroxanthoma is a very rare variant of AFX, with only 13 cases reported to date. The differential diagnoses often include dermal neoplasms composed of clear cells, such as squamous cell carcinoma, basal cell carcinoma, metastatic renal cell carcinoma and balloon cell malignant melanoma. These diagnoses can be ruled out by the typical immunohistochemical profile of clear cell AFX, which is negative for specific epithelial and melanocytic markers. Herein, we describe a rare and unusual case of clear cell AFX arising on the ear of a relatively young adult patient. Histologically, the dermis was completely replaced by an atypical population of vacuolated cells with numerous atypical mitoses. Immunohistochemical stains were negative forpancytokeratin, CK5/6, CK7, and p63 S100 and Melan-A stains. CD10 and CD68 stains were positive, making the findings consistent with the diagnosis of clear cell atypical fibroxanthoma.