A Rare Case of Renal Sarcoma Mimicking Metastatic Osteosarcoma.

Pediatric renal sarcomas are exceedingly rare entities that present diagnostic challenges. We report a remarkable case of a 14-month-old female with an 8 cm right renal mass, accompanied by disseminated bone metastases, posing intricate clinical and histopathological dilemmas. Initial suspicion leaned towards clear cell sarcoma of the kidney (CCSK), however, subsequent histological examination post-chemotherapy revealed high-grade osteosarcoma and further differential considerations arose, including primary renal osteosarcoma and osseous osteosarcoma with secondary renal involvement. Despite inconclusive histology, treatment proceeded with the UH1 chemotherapy protocol for CCSK, incorporating high-dose Methotrexate for potential osteosarcoma, and the patient demonstrated a favorable response to therapy.