Renal collecting duct carcinoma is a rare form of renal cancer known to present in a variety of ways that are often similar to presentations of renal cell carcinoma or transitional cell carcinoma. Little information is available concerning the use of cytology and fluorescence in situ hybridization (FISH) in the diagnosis of collecting duct carcinoma. The available literature contains cases with atypical cytology, but no collecting duct carcinoma cases with abnormal FISH results have been reported. We report a case of renal collecting duct carcinoma presenting with atypical cytology and abnormal FISH results. © 2005 Elsevier Inc.