Primary Bone Sarcoma with Phabdomycosarcomatous Component

Summary We present three cases of primary hone sarcoma with rhabdomyosarcomatous component which in one case appeared in a pure form, i.e.., as rhabdomyosarcoma; in the other two cases it presented as one of multiple components o f the tumor. The first patient was a 70-year-old man with a tumor o f the left femur involving surrounding soft tissue of the thigh. Histologically, this was a case o f so-called dedifferentiated chondrosarcoma with pleomorphic rhabdomyosarcoma representing high grade malignant component. The second patient, a 31-year-old man, developed a tumor in the left tibia which was a rare, fibrosarcoma-like type o f rhabdomyosarcoma. The third patient was a 43-year-old woman with a tumor in the left tenth rib which was shown to be osteo- and chondrosarcoma with a minor rhabdomyosarcomatous component and was classified as malignant mesenchymo ma. All patients were treated by surgery and chemotherapy. The first two o f them died o f metastatic disease 3 months, and 3 years and 4 months following surgery,, respectively. Light microscopical diagnosis of rhabdomyosarcoma on hematoxylin-eosin sections was confirmed immunohistochemically in each case using reactions to desmin, muscle specific actin: and myoglobin, and ultra structurally in two cases. Rhabdomyosarcomatous component in primary bone tumors appears to be rarely present but more cases may be diagnosed in the future, i f immunohistochemical and ultrastructural examinations are to be employed.