Alveolar soft-part sarcoma of the prostate: a case report and review of the literature.

Alveolar soft-part sarcoma (ASPS) is a rare malignant soft tissue tumor of uncertain cellular origin. We reported the case of a 21-year-old man with ASPS presenting itself as a markedly vascular tumor of the prostate. Immunohistochemistry showed positive nuclear staining for TFE3, positive cytoplasm staining for MyoD1 and neuron-specific enolase, and negative for S100, CK, synaptophysin, chromogranin A, myogenin and PSA. A dual-color, break-apart fluorescence in situ hybridization (FISH) assay identified the presence of a TFE3 gene fusion in the tumor cells. RT-PCR was performed to confirm the ASPSCR1 (ASPL)/TFE3 fusion transcript product in the tumor tissue. The patient suffered bone metastases 8 months after surgery and died of cachexia 14 months later. ASPS of the prostate should be discussed in terms of differential diagnosis from clinicopathological characteristics, immunophenotypes, and molecular genetic features.