Clear-Cell Atypical Fibroxanthoma: A Combined Immunohistochemistry Analysis

Atypical fibroxanthoma is considered to be a low-grade sarcoma, characterized by a proliferation of bizarre spindled cells. A case of a rare variant of this tumor, a clear-cell atypical fibroxanthoma, presenting with rapid growth on a 63-year-old female, is reported. The differential diagnosis of a clear cell proliferation and a review of the immunohistochemistry markers used in the diagnosis of atypical fibroxanthoma are discussed. In particular, the usefulness of markers such as CD10, procollagen 1, CD68, CD163, CD99, and S100A6, and the importance of negative markers such as S100, cytokeratin, and desmin are emphasized. Furthermore, the development of a keratoacanthoma at the site of previous Mohs surgery is recounted.