Abstract

Alveolar Soft Part Sarcoma is a rare soft tissue tumor with characteristic histological features, typically seen in children and adolescents, with bad prognosis. These tumors often develop in the deep soft tissues of the lower extremities and body. Although they have a slow clinical course, they have a bad prognosis with late metastases. A 16-year-old girl applied with a complaint of swelling and pain in her left arm. Surgical resection was performed on advanced tumor growth between deltoid and biceps brachio lateralis muscles. Neoplastic development which polygonal cells with wide eosinophilic / clear cytoplasm which are separated histopathologically by vascularized fibrous septa are formed clusters and alveolar like structures, is observed. MyoD1 and CD10 immunohistochemical stains were positive for tumor cells and diastase resident PAS positive cytoplasmic substances were observed in tumor cells. Our case is presented due to rare occurrence and unexpected localization with its’ histopathological and immunohistochemical characteristics and literature review conducted on this subject. ASPS’ diagnosis is possible by interpretation of immunohistochemical findings together with clinical, morphological and architectural findings.