Alveolar soft part sarcoma: a case report with immunohistochemical study.

We report herein, a rare case of a 28 year old Japanese man with alveolar soft part sarcoma. The patient noticed a rapidly growing mass in the inner aspect of his left thigh and a smooth-surfaced, hard nodule revealing bruit on auscultation was found on physical examination. An angiogram showed dense neovascularity from the left profunda femoris artery. Histopathologically, the tumor was composed of nests of tumor cells with hyperchromatic nuclei and vesicular cytoplasm arranged in an alveolar fashion and a histopathologic diagnosis of alveolar soft part sarcoma was made. Immunohistochemically, the tumor cells had desmin and vimentin immunoreactants in the cytoplasm, suggesting muscle origin.