A 15-year-old male presents with an ill-defined, large mass deep in his right thigh. A biopsy is performed, and a representative section is shown here.

Case 22

What is the diagnosis?

A. Burkitt lymphoma
B. Malignant fibrous histiocytoma
C. Leiomyosarcoma
D. Rhabdomyosarcoma
E. Ganglioneuroblastoma





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The diagnosis in this case is rhabdomyosarcoma. Rhabdomyosarcoma is divided into three variants: embryonal, alveolar and pleomorphic rhabdomyosarcoma. The alveolar variant, as shown in this case, commonly arises in the deep musculature of the extremity, and represents 20% of all cases of rhabdomyosarcoma. Histologically, the tumor cells are aligned along fibrous septae that create spaces resembling the alveolar spaces in the lung. The tumor cells are small to moderate in size, with minimal cytoplasm. Prognosis is poor, particularly for tumors which have a t(2;13) translocation.

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