The Role of Immunohistochemistry in the Distinction of Invasive Plasmacytoid Urothelial Carcinoma from its Histologic Mimics

Abstract

Plasmacytoid urothelial carcinoma is a rare and aggressive variant of bladder cancer that is characterized by infiltrating neoplastic cells that closely resemble plasma cells. It may mimic plasmacytoma, lymphoma, and carcinomas such as lobular carcinoma of breast and poorly differentiated carcinomas of gastrointestinal tract secondarily involving the bladder. There is limited data regarding the comparative immunophenotypes of these morphologically similar tumors. The surgical pathology and consultation files at three institutions were searched for plasmacytoid urothelial carcinoma, lobular breast carcinoma and diffuse or signet ring type gastrointestinal carcinoma from 1998 to 2010. H&E slides of 31 cases were reviewed to confirm diagnoses. A focused immunohistochemical panel including antibodies against E-Cadherin, P63, P53, CD138, MUM-1, estrogen receptor (ER), progesterone receptor (PR), GCDFP-15, CA 125, cytokeratin 7 (CK 7), cytokeratin