Vascular invasion in oncocytoma – a case report and review of the literature

Abstract

Introduction Oncocytoma of the kidney is a benign neoplasm that is composed of large cells with abundant eosinophilic granular cytoplasm, which represent numerous enlarged mitochondria. This tumour is thought to arise from intercalated cells of the collecting duct. Case report A 60-year-old Egyptian male, with no significant past medical history, was found to have a renal mass on elective radiology scan. He had a family history of a brother with renal cell carcinoma. Pathological findings Macroscopic examination showed a radical nephrectomy with a well-circumscribed 50 × 50 × 40 mm, non-encapsulated mahogany-brown tumour. There was no central scar. Tumour bulged against the renal pelvis and sinus fat with suspicious renal vein invasion. Microscopically, there was an epithelial tumour composed of cohesive nests with microcyst formation, surrounded by oedematous stroma. Tumour cells had round nuclei, inconspicuous nucleoli and moderate amounts of granular cytoplasm. There was evidence of vascular invasion, with a 10 mm plug of tumour with a pushing margin in one renal vein tributary in the renal sinus fat. There was no necrosis or perinephric or sinus fat involvement. The renal vein resection margin was clear. The diagnosis was oncocytoma. Discussion Oncocytoma comprises approximately 5% of kidney tumours in adults. The mean age at presentation is in the seventh decade of life; and males are affected thrice as often as females. Most occur sporadically. The majority are asymptomatic at presentation and diagnosed during radiographic work-up of unrelated conditions. A few patients present with haematuria, flank pain or a palpable mass.