Dedifferentiated chondrosarcoma arising in a solitary osteochondroma with leiomyosarcomatous component: a case report

Background A rare variant of dedifferentiated chondrosarcoma with leiomyosarcomatous component in a 63-year-old male is reported. Case report He had a life-long osteochondroma adjacent to the left knee and recently developed swollen and pain. We initially suspected an intermediate grade chondrosarcoma arising in a solitary osteochondroma, but a biopsy specimen revealed a dedifferentiated component that histologically was classified as leiomyosarcoma. Multiple lung metastases were also present. The patient underwent amputation above knee and lung operation following adjuvant chemotherapy, but he died because of pulmonary metastasis 2 years after first admission. Discussion The differentiated component usually shows the histological features of osteosarcoma, malignant fibrous histiocytoma, and fibrosarcoma. Among the rare dedifferentiation with leiomyosarcomatous component, case arising in a solitary osteochondroma is not reported yet.