Metastatic plasmacytoid urothelial carcinoma: a case report and review of the literature.

Plasmacytoid urothelial carcinoma is a rare form of invasive urothelial carcinoma first described in 1991 by Sahin et al. [Acta Cytol 1991;35:277-280]. Since this original publication, over 70 cases of plasmacytoid urothelial carcinoma have been described. A small number of cytologic descriptions have been published, including cases involving cerebrospinal fluid cytology, bladder washings and urine cytology. To our knowledge, we describe the first fine needle aspiration of metastatic plasmacytoid urothelial carcinoma in a 75-year-old man who presented with a pathologic fracture of the L4 vertebral body. One of the diagnostic pitfalls in the cytologic evaluation of this rare malignancy is the positive staining with CD138. While CD138 is a marker for plasma cell differentiation, it is also positive in plasmacytoid urothelial carcinoma. In addition to recognizing the cytomorphologic details, a full immunohistochemical panel is helpful in properly characterizing this entity. A brief discussion of long-term prognosis and treatment benefit is provided.