Rhabdomyosarcoma of the Long Bone in an Adult

Rhabdomyosarcoma is one of the most common sarcomas of childhood. It usually arises in the soft tissues but may involve bone by several different mechanisms, includ ing direct extension, metastatic spread, as a component of dedifferentiated chondrosar coma or malignant mesenchymoma, or as a primary tumor. Only nine cases of primary rhabdomyosarcoma of bone have been previously reported, many of them not well documented. The histologic, immunohistochemical, and ultrastructural findings of a primary rhabdomyosarcoma of the femur in a 68-year-old woman are presented. Also discussed are the different aspects of skeletal muscle differentiation in bone tumors and the possible explanation for the rarity of primary skeletal rhabdomyosarcoma. Int J Surg Pathol 1(4):253-260, 1994