Primary renal osteosarcoma.

Objectives To investigate primary osteosarcoma (osteogenic sarcoma) of the kidney, a rare and aggressive neoplasm. Methods We present clinical and pathologic features of three female patients, aged 50, 66, and 78 years, affected by primary osteosarcoma of the kidney. The diagnosis was made by H&E-stained samples from totally (cases 1 and 2) or partially (case 3) embedded tumors. Results Reported cases showed histologic features of low-grade (n = 1), chondroblastic (n = 1), and osteoblastic (n = 1) osteosarcoma. Tumor size ranged from 3 to 7 cm, and pT category was pT1a (n = 1), pT1b (n = 1), and pT3a (n = 1). Immunohistochemistry gave focal positive results with PAX2 and CD10 in case 1 and S100 in case 2. On follow-up, two patients were disease free at 25 and 68 months and one died of metastases. Conclusions Surgically treated primary renal osteosarcoma might not be as aggressive as previously thought if diagnosed early with low pT status.