Alveolar soft part sarcoma of the larynx: A case report of an unusual location with immunohistochemical and ultrastructural analyses

BACKGROUND: Alveolar soft part sarcoma (ASPS) is a rare mesenchymal neoplasm of uncertain origin. In this article, we report a case of ASPS occurring in the larynx, an extremely rare location for this rather unusual tumor. METHODS AND RESULTS: The patient was a 34-year-old Japanese woman who requested an examination for hoarseness. The tumor showed a proliferation of large polygonal cells with periodic-acid-Schiff-positive diastase-resistant intracytoplasmic granules, arranged in an alveolar growth pattern. The cytoplasm of the tumor cells was eosinophilic. Tumor cells were positive for vimentin and titin. Nuclear immunoreactivity for TFE3 was observed, and the Ki-67 labeling index was 14.7%. Ultrastructurally, electron-dense rod-shaped crystals were infrequently observed in the cytoplasm. This case was finally diagnosed as ASPS of the larynx. CONCLUSION: We discuss the histogenesis and differential diagnosis of ASPS with immunohistochemical and ultrastructural findings. TFE3 immunohistochemistry was found to be a very useful marker for the diagnosis of ASPS.