Bilateral metachronous periosteal osteosarcoma.

The first case of bilateral metachronous periosteal osteosarcoma (OS) is reported. A 14-year-old white boy presented with a 1-month history of pain and swelling in his right thigh. Periosteal OS was diagnosed on a basis of the radiologic and pathologic findings. Treatment was with local resection and total hip replacement after a short course of high-dose methotrexate; multi-agent chemotherapy was continued postoperatively for 3 months. He remained well for 3 years. He then represented with a mass in the left femur that had been slowly growing for about 1 year. Radiologic and biopsy studies showed periosteal OS. Full investigations showed no evidence of metastatic disease. Treatment consisted of local resection without chemotherapy. He remained well for 6 months after the second excision until developing multiple pulmonary metastases. All further therapy was refused. The question as to whether the second tumor was a new primary lesion or a metastasis is discussed, together with possible differential diagnoses.