Plasmacytoid urothelial carcinoma--diagnostic challenge in cytology.

Plasmacytoid urothelial carcinoma (PUC) is a very rare variant of urothelial carcinoma with an aggressive clinical course. According to small series reported to date, it is a high grade cancer usually diagnosed at an advanced stage, and with poor prognosis. Descriptions of the cytologic features of this type of carcinoma in literature are limited. Plasmacytoid appearance of tumor cells could cause diagnostic dilemma and potential incorrect diagnosis as multiple myeloma (MM). This report describes cerebrospinal fluid, bone marrow, and urine sediment cytomorphologic and immunocytochemical findings in a patient with meningeal carcinomatosis as the first manifestation of a PUC, initially misdiagnosed as MM with a brief review of the literature.