Plasmacytoid Urothelial Carcinoma: An Unusual Variant That Warrants Aggressive Management and Critical Distinction on Transurethral Resections.

Plasmacytoid urothelial carcinoma (PUC) is a variant of infiltrating urothelial carcinoma that is characterized by tumor cells that have striking morphologic resemblance to and immunohistochemical overlap with plasma cells, and that harbors CDH1 mutation. Plasmacytoid urothelial carcinoma can be widely infiltrative and may permeate the urinary bladder in a linitis plastica-like manner and spread along the fascial planes and into the peritoneum. Compared with conventional urothelial carcinoma, PUCs have greater chance for higher-stage disease, surgical margin positivity, and metastasis at presentation that translate into its poorer outcome. Upstaging of lamina propria-invasive (pT1) tumors diagnosed at transurethral resections is common. Because of its unfavorable behavior, a more aggressive management approach is being recommended for PUC, including consideration for upfront cystectomy in pT1 tumors. Thus, accurate distinction should be made especially on the initial transurethral resection specimens because of the therapeutic and prognostic implications. Awareness of PUC's unique clinical presentation, morphology, and immunohistochemical profile is important to avoid a potential misdiagnosis from its mimics.