Abstract

Background: Primary osteosarcoma of the kidney is an extremely rare malignant neoplasm, accounting for less than 1% of all primary renal tumors. To the best of our knowledge, fewer than 30 cases have been reported in the literature since 1936. The disease is usually diagnosed at an advanced stage, and approximately 32% of patients present with metastasis; therefore, the overall prognosis is very poor. Treatment strategies such as surgery, chemotherapy, and radiotherapy mainly have a palliative role in this tumor. Case presentation: In this article, we present a case of primary renal osteosarcoma in a 56-year-old male patient. The patient underwent total nephrectomy followed by chemoradiotherapy. After treatment, the patient’s general condition remained stable, with no treatment-related complications. The tumor-free survival recorded to date is 1 year. Conclusion: Definitive diagnosis should be based on the integration of clinical context, imaging findings, histopathology, and immunohistochemistry. Because this is an extremely rare entity, pathologists should perform careful gross examination and thorough sampling, while considering other differential diagnoses, particularly sarcomatoid carcinoma, to avoid misdiagnosis.