Oncocytic Form of Papillary Renal Cell Carcinoma: A Rare Morphological Variant

Oncocytic Papillary Renal Cell Carcinoma (OPRCC) is a rare variant of Papillary Renal Cell Carcinoma (PRCC), characterised by distinct morphological and immunophenotypic features. Present report is of a 75-year-old hypertensive female who presented with constipation and abdominal bloating for four months. Imaging revealed an exophytic lesion in the lower pole of the right kidney, measuring 6.1×5.8×5.4 cm, without perinephric or sinus invasion. Laboratory studies demonstrated mild haematuria, elevated Lactate Dehydrogenase (LDH), and hypercalcaemia. The patient subsequently underwent radical nephrectomy. Gross examination revealed a 6.5 cm brown-yellow tumour with haemorrhagic areas, confined to the kidney. Histopathology showed papillary structures lined predominantly by oncocytic cells with abundant granular eosinophilic cytoplasm, vesicular nuclei, and prominent nucleoli. Focal pseudostratification, nuclear atypia, haemosiderin deposition, foamy macrophages, and focal necrosis were present, with no capsular, vascular, or nodal involvement. Immunohistochemistry (IHC) demonstrated diffuse positivity for Alpha-MethylacylCoA Racemase (AMACR), vimentin, and CD10, with negativity for CK7, CD117, and Ki-67, confirming the diagnosis of OPRCC. Postoperative recovery was uneventful, and a structured surveillance plan was initiated. Recognition of OPRCC is crucial to prevent misdiagnosis with benign oncocytoma or more aggressive RCC subtypes, enabling appropriate prognostication and management.