Low-grade oncocytic fumarate hydratase-deficient renal cell carcinoma in a pediatric liver transplant recipient: a case report.

Fumarate hydratase (FH)-deficient renal cell carcinoma (RCC) is a rare molecularly defined neoplasm, reported only occasionally in children. We describe a 9-year-old liver transplant recipient with prior lymphoma, chronic immunosuppression, hypertension, and reduced renal reserve who presented with a complex cystic left upper-pole renal mass. Open partial nephrectomy was performed using local parenchymal compression without hilar clamping to avoid global ischemia. Histopathology confirmed low-grade oncocytic FH-deficient RCC (pT1a, R0), and renal function remained stable. Germline FH sequencing identified a variant of uncertain significance, warranting genetic counseling, variant reinterpretation, and long-term surveillance.