Atypical fibroxanthoma of the scalp with recurrent and multiple regional cutaneous metastases

AFX: atypical fibroxanthoma BCC: basal cell carcinoma PDS: pleomorphic dermal sarcoma SCC: squamous cell carcinoma INTRODUCTION Atypical fibroxanthoma (AFX) is a neoplastic skin disease that arises from myofibroblasts and most commonly occurs in elderly patients on sun-exposed skin. Immunohistochemistry is commonly used to make the diagnosis of AFX. Findings are positive for vimentin, CD10e, CD68, and actin and negative for CAM5.2, CD34, melan-A, S100 protein, HMB45, and cytokeratin A1/A3. AFX is a low-grade malignancy with rare metastases (1% of cases) that usually occur within a short period. The risk of metastasis is increased by tumor depth, vascular invasion, and cutaneous tumor recurrence. In the World Health Organization revised classification of soft tissue tumors in 2013, pleomorphic dermal sarcoma (PDS) was recognized as a distinct diagnostic entity. Previously, PDS was placed in the category of malignant fibrous histiocytoma, a term that has been deleted and replaced by undifferentiated sarcoma. Histologically, AFX cannot be distinguished from a pleomorphic superficial form of PDS. Often the clinical course and involvement of tumor invasion of subcutaneous tissue guides the diagnosis. This report will (1) show an approach to diagnosing AFX, (2) report a case of AFXwithmultiple intransit metastases over a 20-month period, and (3) highlight the updated terminology for fibrohistiocytic tumors of undetermined lineage.