Supplementary Material for: Osteosarcoma arising from iliac bone lesions of hereditary multiple osteochondromas: A case report

Osteochondromas are benign tumors that arise primarily in the epiphyseal region of long bones. The malignant transformation rate, mainly to chondrosarcoma, is estimated to be less than 1-3% [1]. Transformation to osteosarcoma is very rare, having been reported only 13 times. Little information is available on treatment or outcome.
A case of osteosarcoma arising in hereditary multiple osteochondromas of the right iliac bone in a 66-year-old woman is reported. After one course of chemotherapy with doxorubicin and ifosfamide, extensive resection of the tumor was performed. The pathology showed proliferation of highly pleomorphic dysplastic cells with bone formation inside the tumor just below the osteochondroma tissue, which led to the diagnosis of osteosarcoma arising from the osteochondroma. One and a half years have passed since the surgery, and no recurrence or metastasis has been observed, but further follow-up is necessary due to the short time after surgery.