Primary osteosarcoma of the kidney. Case report and review of literature.

Primary osteosarcoma of the kidney is an extremely rare phenomenon with less than 20 previously reported cases in the English literature since 1936. Diagnosis usually is made in advanced stages of disease with weight loss, palpable tumor, flank pain and gross hematuria being the characteristic features of clinical presentation. Radiographically bizarre renal calcifications may be suggestive of this uncommon neoplasm. The atypic location is explained by metaplastic changes of originally primitive embryonic mesenchymal tissue. Though the primary treatment for sarcomas is surgical resection, because of their usual late and high stage presentation multimodal adjuvant therapy may be desirable. We describe the clinical course of a 48-year-old male patient with a primary renal osteosarcoma discovered by ultrasound. A marked reduction of vital tumor cells and an impressive increase of neoplastic bone formation following polychemotherapy is demonstrated histopathologically. The principal clinical findings, differential diagnosis, etiology, pathogenesis and treatment modalities of this uncommon malignancy are discussed.