PrimaryAlveolar SoftPartSarcoma (ASPS)oftheBreast Report ofa Deceptive Casewith Xanthomatous Features Confirmed byTFE3Immunohistochemistry andElectron Microscopy

Alveolar soft partsarcoma (ASPS) isarareneoplasm that mostcommonly presents inthelowerextremities. Although ASPShasdistinctive histologic features, itmay causediagnostic problems whenitarises inunusual locations. Toourknowledge, only1caseofASPSarising within thebreast haspreviously beenreported. Here, we report asecond caseofprimary mammaryASPS.Thepatient wasa44-year-old womanwhopresented withabreast mass.Needle biopsy wasperformed, yielding a polygonal cell lesion withabundant, predominantly xanthomatous cytoplasm. The cells labeled strongly forthehistiocytic markerCD68,suggesting abenign macrophage-rich lesion. However, theunusual nature ofthelesion aswellasthe prominence ofnucleoli prompted suggestion foranexcision. Theexcision more clearly revealed thelesion's alveolar architecture anddemonstrated cells withmore