Low-grade Collecting Duct Carcinoma Of The Kidney: A Potential Mimic Of Conventional Clear Cell Carcinoma

Abstract

Collecting duct carcinoma of the kidney is a well-known, but relatively uncommon tumor characterized by a high cytologic grade, desmoplastic stroma and a poor clinical outcome. Since 1979, however, there have been several reports of low-grade renal carcinoma of putative collecting duct origin. These low-grade tumors were extensively papillary, tubulopapillary or tubulocystic, with a low nuclear grade (usually Furhman grade 1 or 2). Most have conferred a benign follow-up course, even when treated only by partial nephrectomy. The previous reports of such tumors have been variably characterized immunohistochemically and ultrastructurally. We report the cases of a low-grade renal carcinoma of collecting duct origin, arising in the right renal lower pole of a 47-year-old-male with a history of gout and nephrolithiasis. Microscopically, the tumor showed a tubular and tubulocystic pattern and was composed almost exclusively of clear cells, closely mimicking conventional (clear cell) renal cell carcinoma. Tumor cells stained positively for PAS, showed droplet-like staining with Hale\'s colloidal iron, were variably alcian blue positive and were mucicarmine negative. They were reactive with immunohistochemical antibodies to peanut agglutinin (PNA), Ulex europaeus-1 agglutinin (UEA-1), pan-cytokeratin, CAM 5.2, cytokeratin 7, epithelial membrane antigen (EMA) and vimentin. Electron microscopy showed microvillous-lined tubules, desmosomes, and tonofilaments, with a paucity of mitochondria. The patient was treated by partial nephrectomy and has been without evidence of disease for a follow-up period of 10 months.