Primary Alveolar Soft Part Sarcoma of Bone: A Rare Occurrence in 8 Patients, Posing a Diagnostic Challenge

Abstract

Context.— Alveolar soft part sarcoma is a rare soft tissue tumor involving mainly deep soft tissue of the lower extremities. Primary bone involvement is extremely rare. Objective.— To discuss histopathologic and immunohistochemical features of alveolar soft part sarcoma along with challenges in diagnosis and management in the context of primary bone origin. Design.— Our study constituted 8 patients. Data were collected from the Tata Memorial Hospital, Mumbai, India, during a 10-year period. Results.— Five patients in our study were female and 3 were male. Their ages ranged from 13 to 56 years. Primary bone involvement was seen in the humerus, tibia, fibula, radius, calcaneus, and rib. Radiologic impression was that of a primary malignant bone tumor in all patients. Conventional histopathologic features were seen in 7 of 8 patients. Positive immunohistochemical expression for TFE3 was demonstrated in 6 patients. All patients had distant metastasis either at presentation or later in the course of the disease. Surgical excision of the primary tumor and adjuvant chemotherapy formed the basis of treatment. Four patients succumbed to disease and 2 were alive with disease. Conclusions.— Rare occurrences of primary bone alveolar soft part sarcoma posed a diagnostic challenge in the form of differential diagnoses of metastatic tumors resembling it either morphologically or immunohistochemically. The combined application of clinical and radiologic features along with characteristic histomorphology and immunohistochemistry helps to arrive at a definite diagnosis of alveolar soft part sarcoma. Aggressive behavior of this tumor and its refractoriness to conventional chemotherapy were evident from our series.