Extraskeletal osteosarcoma arising in the buttock.

Extraskeletal osteosarcoma is a rare sarcoma that accounts for about 1% of malignant soft tissue tumours. We report an very unusual case of a small-size extraskeletal osteosarcoma arising in the superficial subcutaneous region of the buttock. The patient was a 55 year-old female. She incidentally noticed a small nodule in the right trochanteric region. It was removed under local anesthesia at a private clinic. An additional wide excision was performed at our hospital. There was an 8 mm? 10 mm mass in the subcutaneous tissue. No invasion of the underlying fascia was observed. Microscopic examination of the removed tumour showed bizarre-looking spindle and giant cells with lace-like osteoid. The tumour was diagnosed as extraskeletal osteosarcoma. Chemotherapy with Rosen T-20 was administered to the patient. The patient has survived without recurrence or metastasis for 4 years since the primary surgery. Its superficial location, very small size, wide excision, and chemotherapy were thought to contribute to her long survival.