Alveolar soft part sarcoma presenting with cutaneous metastases: Report of a case with immunohistochemical and molecular characterization

Alveolar soft part sarcoma (ASPS) is an uncommon neoplasm of uncertain histogenesis that usually behaves as a painless, slow-growing mass that metastasizes early. We report a 21-year-old woman with cutaneous metastases of ASPS, whose histologic characteristics gave rise to a wide range of differential diagnoses of both primary and metastatic cutaneous neoplasms. The tumor failed to show a characteristic immunoprofile using routine immunohistochemical procedures, but was strongly and diffusely positive for the TFE3 antibody. The molecular study identified a type 2 alveolar soft part locus-transcription factor E3 (ASPL-TFE3) fusion, secondary to der(17)t(X;17)(p11.2;q25) translocation. A computed tomography scan performed after the diagnosis was made disclosed a 13-cm primary tumor in the left buttock. Cutaneous metastases presenting as the first sign of ASPS have not been reported previously. We emphasize the difficulties in making the diagnosis of ASPS when it presents in an unusual manner.