Plasmacytoid urothelial carcinoma of the bladder.

In this report, we present the clinicopathologic features of 11 cases of the plasmacytoid variant of urothelial carcinoma. This is a rare variant of bladder cancer recognized by the current World Health Organization classification of urologic tumors. The plasmacytoid component varied from 30% to 100% of the tumor specimen; in 8 cases, the plasmacytoid component comprised greater than 50% of the tumor with 2 cases showing pure plasmacytoid carcinoma. The architectural pattern of the tumor varied from solid expansile nests with noncohesive cells to mixed solid and alveolar growth; a streaking discohesive architecture was additionally present in 2 cases (18%). At histology, the individual tumor cells had an eccentrically placed nucleus and abundant eosinophilic cytoplasm reminiscent of plasma cells. Most neoplastic cells had nuclei of low to intermediate nuclear grade with occasional nuclear pleomorphism. Seven of 9 mixed cases had concurrent conventional high-grade urothelial carcinoma, and the remaining 2 cases presented features of nested or micropapillary urothelial carcinoma. Small intracytoplasmic vacuoles were variably present in all cases. All patients had advanced stage cancer (>pT3), and 8 (73%) had lymph node metastasis. Immunohistochemical staining demonstrated that both plasmacytoid and associated conventional urothelial carcinoma were positive for cytokeratins 7, 20, and AE1/AE3 and epithelial membrane antigen; CD138 was positive in 3 cases. Follow-up information was available in all cases (range, 2-16 months; mean, 7 months). Nine of the patients died of disease from 2 to 11 months, and 2 patients were alive with disease at 8 and 16 months. In summary, plasmacytoid variant of urothelial carcinoma is an aggressive variant associated with poor prognosis that presents at an advanced clinical stage. In limited samples, it may be misdiagnosed as chronic cystitis or plasmacytoma, a pitfall further compounded by CD138 expression in some cases. Morphological distinction from other malignant neoplasms with plasmacytoid phenotype is critical for its clinical management.