Chondroblastic variant of extraskeletal osteosarcoma of thigh: A rare case report

Extraskeletal osteosarcoma (ESOS) is a rare, malignant neoplasm comprising 1% of mesenchymal tumors. We hereby report a case of ESOS of the thigh which was diagnosed on histopathology. Magnetic resonance imaging showed two lobulated markedly heterogeneous masses in the subcutaneous fat of the lateral aspect of thigh measuring 5 cm × 4.2 cm × 4.2 cm and 7.1 cm × 5.7 cm × 6.0 cm. Femur and major neurovascular bundles were unremarkable. Excision biopsy revealed a circumscribed tumor comprising sheets and fascicles of spindle cells and abundant osteoid produced directly by malignant cells. Malignant cartilage and extensive areas of calcification were also seen. Hence, a diagnosis of ESOS was given. Prompt diagnosis and surgical resection are mandatory, because unlike conventional osteosarcoma, ESOSs are more aggressive and do not respond to chemotherapy.