Cytologic Findings of a Plasmacytoid Variant of Urothelial Carcinoma of the Urinary Bladder in Voided Urine

The plasmacytoid variant is an extremely rare form of urothelial carcinoma in which the malignant cells resemble those of plasmacytoma. We report the cytologic features of 3 cases of this disorder. All 3 patients were male and presented with painless macroscopic hematuria. The voided urine cytology revealed a few scattered clusters of tumor cells in a bloody background. Each tumor cell had an abundant amount of cytoplasm that was clear or densely stained and characterized by eccentrically located nuclei. A histological examination of tissue obtained from a radical cystectomy confirmed the cytologic diagnosis in each 3 case, revealing a diffusely infiltrating tumor composed of round, noncohesive tumor cells demonstrating a high nuclear grade. These cells had infiltrated the tunica propria in 2 cases, but were limited to the submucosa in 1 case. The tumor cells were plasmacytoid in appearance, each demonstrating an eccentric nucleus and dense cytoplasm, as seen in the cytologic findings. All of the tumors were immunoreactive for pancytokeratin, CK7, CK20; negative for epithelial membrane antigen (EMA), leukocyte common antigen (LCA), kappa, lambda, and CD79a. Thus, it is important to consider the plasmacytoid variant of urothelial carcinoma in addition to plasmacytoma or lymphoma as a diagnosis when encountering plasmacytoid tumor cells in a voided urine sample.

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