A cystic non-Wilms renal tumor in a Nepalese boy: A rare case of clear cell sarcoma

INTRODUCTION: Clear cell sarcoma of the kidney (CCSK) is an uncommon childhood malignancy known for its aggressive behavior and tendency to recur and metastasize to the brain and bones. CASE PRESENTATION: We report a four-year-old boy evaluated for non-specific abdominal pain with an incidental radiological finding of a right lower pole cystic renal mass initially thought to be cystic Wilms' tumor. A pretherapy core biopsy of the mass suggested a clear cell tumor. An open transperitoneal radical nephroureterectomy with aortocaval lymph node sampling was done. Based on histopathological findings and immunohistochemical analysis, CCSK was diagnosed. Appropriate chemotherapy and radiotherapy were instituted postoperatively. At six years follow-up, he was tumor-free and doing well. CLINICAL DISCUSSION: The workup for CCSK includes diagnostic and metastatic imaging, histopathology, and immunohistochemistry analysis. Diagnostic segregation of CCSK and Wilms' tumor is imperative to institute optimal oncological management and improve overall treatment outcomes. CONCLUSION: Considering the age of presentation and clinico-radiological appearance, CCSK can be mistaken for Wilms' tumor, which is much more common in occurrence despite the distinguishable histopathological features, treatment modalities, and prognosis.