Sandbox: DDx Kidney mass

• 50-70 yo males
• Asymptomatic
• Incidental finding

• Palpable flank mass

• Heterogeneous, multifocal, well-circumscribed, large mass on CT
• Less intense contrast enhancement
• Distinct fibrous capsule
• Calcification

• Papillary fibrovascular cores
• Foamy macrophages
• Intracellular hemosiderin
• Longitudinal nuclear groove
• Hyaline globules present

• Trisomy 7
• Trisomy 17

Nonmalignant causes

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