Cutaneous Extraskeletal Osteosarcoma on the Scar of a Previous Bone Graft

Extraskeletal osteosarcoma (ESOS) is a very rare malignant tumor of mesenchymal origin. It is rarer than osseous osteosarcoma and there are very few reports of the skin being a primary site. Most reported cutaneous ESOS were accompanied with metastasis in other organs. A 56-year-old man presented with a painful, 1.5×0.8 cm sized, brown-colored nodule on the right girdle area for 3 months. The histologic findings revealed a tumor that was confined to the dermis without connection to the subcutaneous tissue. In addition, there were large amounts of thin and lace-like bony trabeculae and osteoid with neoplastic cells in a highly pleomorphic sarcomatous stroma.