Extraskeletal osteosarcoma: report of a case with unusual imaging features and histopathological correlation

Extraskeletal osteosarcoma (ESO) is a rare malignant mesenchymal neoplasm that produces osteoid or bone and/or cartilage and lacks skeletal involvement. Reports in the radiological literature are scarce, and most case reports are focused on mineralized lesions. However, half of the lesions are not calcified or ossified, rendering the radiological differential diagnosis with other soft tissue tumors very difficult.