Non-Invasive Papillary Urothelial Carcinoma With “Plasmacytoid” Morphology: A Retrospective Review of 500 Consecutive Specimens

We have anecdotally encountered non-invasive (pTa) papillary urothelial carcinomas (PUCs) with eccentric nuclear localization and eosinophilic globular cytoplasm, imparting a "plasmacytoid" appearance, with inconsistent grading in clinical practice. These tumors lack conventional high-grade cytologic features, but show concerning architectural disorder for low grade; in some, associated subsequent invasive carcinoma was identified. Herein, we investigate the frequency of such pTa PUC, their progression rate, and other adverse subtype histology. A retrospective review of 500 consecutive specimens of transurethral resections/biopsies of pTa PUC was performed and evaluated for the presence of "plasmacytoid" morphology. Clinical follow-up was performed. Exclusion criteria included any pTa PUC containing World Health Organization 2004 high-grade cytology, concurrent carcinoma in situ, concurrent invasion, or any prior invasive urothelial carcinoma. Twenty-two of 500 pTa PUC containing plasmacytoid morphology were identified (rate of 3.4%) from 17 patients with a mean age of 67 years. The extent of plasmacytoid morphology ranged between 5% and 95% (mean = 60.6%). Follow-up was available for 15/17 patients (range 3.1-40.1 months; mean = 18.1 months). Subsequent intravesical treatments included: chemotherapy (n = 7), BCG (n = 4), chemotherapy and BCG (n = 2), surveillance (n = 2), immunotherapy/BCG (n = 1), BCG/immunotherapy/chemotherapy (n = 1). Two of 15 patients showed disease progression (13.3%), one progressing to pT1 (at 1.9 months) and one who developed liver metastasis (at 30.2 months). While pTa PUC with "plasmacytoid" morphology is uncommon, a subset may show disease progression, including metastasis. Further studies are needed to establish whether "plasmacytoid" morphology in pTa PUC should be considered low versus high grade or an intermediate grade.