Sandbox: DDx Kidney mass

• 50-60 yo male
• Asymptomatic
• Incidental finding on imaging
• May have hematuria and flank pain
• Palpable flank mass

• Cells arranged in nests
• Granular eosinophilic cytoplasm
• Nuclei uniform and round with no pleomorphism

Nonmalignant causes

anaplastic sarcoma clear cell sarcoma mesoblastic nephroma metanephric stromal tumor nephroblastomatosis / nephrogenic rests neuroblastoma oncocytoid carcinoma after neuroblastoma ossifying