Intramammary Angiomatoid Fibrous Histiocytoma, a Rare EWSR1 Rearranged Mesenchymal Neoplasm in a Previously Unreported Anatomic Location with Review of the Cleveland Clinic Experience

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor that is most commonly reported to arise in the subcutaneous tissues of the upper extremities in adolescents and young adults. At present, the WHO classifies this neoplasm as a tumor of uncertain differentiation. AFH is most often clinically regarded as a tumor of intermediate risk due to low reported rates of recurrence and only rare occurrences of metastases. Its histomorphological hallmarks are a prominent lymphoid cuff surrounding a spindle cell neoplasm with syncytial-appearing cytoplasm. Several variant morphologies have been described. Genetically, the tumor is characterized by translocations involving the EWSR1 gene in over 90% of cases. A widening range of anatomical locations and morphological variants of AFH has been reported in the literature; however, neither anatomic location nor specific morphologic features have been shown to correlate with clinical/biological behavior. We report a unique case of AFH arising in the parenchyma of the breast. The neoplasm showed the typical histomorphology including a peripheral lymphoid cuff. The lesional cells in this case were found to be immunoreactive with desmin, and a positive EWSR1 result was confirmed by break-apart fluorescence in situ hybridization testing. To our knowledge, this is the first report of AFH arising in the breast parenchyma of a postmenopausal female.