Cystic Nephroma: A Histologic and Immunohistochemical Study of 10 Cases

Abstract

Abstract Context.—Cystic nephroma is a rare and controversial benign multicystic renal tumor. While the clinical, radiologic, and histologic features of cystic nephroma are well described, the immunohistochemical features are not. The role of immunohistochemistry in the differential diagnosis, which includes multicystic renal cell carcinoma, is also unknown. Objective.—To define the histologic and immunohistochemical features of cystic nephroma. Design.—Ten cases of cystic nephroma diagnosed at 2 institutions during a period of 10 years were stained with an immunohistochemical panel consisting of 20 immunostains. Results.—Median age at diagnosis was 61 years, with a range from 31 to 79 years. The female-to-male ratio was 9:1. Grossly, the tumors were multicystic masses without solid nodules. Histologic features included cysts lined by flat, cuboidal, or hobnail epithelium and septa variably lined by fibrous (10/10 cases) and/or ovarian-like (7/10 cases) stroma. Corpus albicans–like acellular hyalinized structures were noted in the septa in 9 of 10 cases. The cyst epithelium showed consistent positivity for distal tubule/collecting duct markers (cytokeratin 19, cytokeratin AE1/AE3, epithelial membrane antigen) and variable positivity for proximal tubule markers (α1-antitrypsin, lysozyme, CD15, CD10). The ovarian-like stroma (present in 7/10 cases) stained positively for progesterone receptors (6/7 cases) and estrogen receptors (4/7 cases). Conclusions.—Our immunohistochemical findings confirm a previous report of both distal tubule/collecting duct and proximal tubule differentiation in cystic nephroma. Stromal estrogen and/or progesterone receptor positivity in the majority of cases of cystic nephroma is a novel finding.