Osteosarcoma of the patella: a case report.

We present a rare case of osteosarcoma involving the patella. A 30-year-old Japanese woman first consulted our out-patient clinic with a 2-year history of knee pain. Radiographs showed an enlargement of the patella with irregular distribution of both osteolytic and sclerotic lesions. Computed tomography and magnetic resonance imaging demonstrated soft tissue extension at the anterior part of the patella. Incisional biopsy showed abundant osteoid formation by spindle-shaped malignant cells, and the histological diagnosis was conventional osteosarcoma. The patient underwent preoperative chemotherapy, but there was no response. Furthermore, she developed a pathological fracture during chemotherapy. She underwent above-the-knee amputation with postoperative chemotherapy. She developed multiple metastases in the thoracic vertebrae 20 months after the surgery. At the most recent examination, she remains alive with multiple spinal metastases without paralysis 4 years after the surgery.