Case 12 -

Tubulocystic Carcinoma John N Eble, M.D. Holger Moch, M.D.

Case history: A 27-year-old man developed flank pain after moving some boxes. His hematocrit dropped abruptly and radiography revealed a large mass in the inferior pole of his left kidney. Radical nephrectomy was done. Macroscopic findings: There was an 18 cm pocket in the perirenal fat which was filled with blood and a spongy tan ovoid 7 cm mass in the lower pole of the kidney. Diagnsosis: Tubulocystic carcinoma Tubulocystic carcinoma is an emerging entity and little has been published about it. The first illustration and description was by Pierre Masson in the early 1950's and he called it "bellinian epithelioma." George Farrow described and illustrated this tumor in the third series AFIP fascicle and considered them to be collecting duct carcinomas. Later Farrow published a couple of cases along with some other types of tumors in an article in Urology and used the word "tubulocystic" for them. Gross Pathology These tumors are composed of many cysts, often of relatively uniform and of small size. The cysts are surrounded by delicate septa and contain clear watery fluid. Microscopic Pathology The cysts are lined by a single layer of cells with eosinophilic or amphophilic cytoplasm. The nuclei are roughly spherical and usually contain large nucleoli which are readily visible with a 10x objective. Mitotic figures are uncommon. Tiny cysts and solid clusters of epithelial cells are sometimes seen at the periphery of the tumor. Mostly, the tumors are well-circumscribed but invasion into perinephric fat has been seen. References: Masson P. Tumeurs humaines, 1955. In: Kobernick S, editor. Human Tumors, Diagnosis and Technique. 20 ed. Detroit: Wayne State University Press; 1970. p.740-1. Murphy WM, Beckwith JB, Farrow GM. Atlas of Tumor Pathology, Third Series, Fascicle 11, Tumors of the Kidney, Bladder, and Related Urinary Structures. Washington, D.C.: Armed Forces Institute of Pathology; 1994. MacLennan GT, Farrow GM, Bostwick DG. Low-grade collecting duct carcinoma of the kidney: report of 13 cases of low-grade mucinous tubulocystic renal carcinoma of possible collecting duct origin. Urology 1997;50:679-84.