Extramedullary plasmacytoma invading the bladder: case report and review of the literature.

Multiple myeloma is characterized by neoplastic proliferation of a single clone of plasma cells engaged in the production of a monoclonal protein. This condition affects mainly the bone marrow, but extramedullary manifestations can be seen in any organ. Urinary bladder involvement is extremely rare, with only 14 cases reported in the literature to our knowledge. Herein, we report a large extramedullary bladder plasmacytoma arising in a patient with history of multiple myeloma. A 78-year-old woman with history of multiple myeloma, currently in remission, presented with a large intravesical tumor. Because the tumor was considered to have characteristics of anaplastic neoplasm from transitional cell origin with evidence of deep muscular invasion, a radical cystectomy was performed. A subsequent microscopic evaluation of the cystectomy specimen revealed round cells with an eccentric cartwheel-like nucleus suggestive of plasmacytoma. The diagnosis was further confirmed with immunohistochemical studies. It is difficult, according to the literature, to distinguish bladder plasmacytoma from anaplastic transitional cell tumors. It is important to provide the pathologist with an appropriate history and to have a high index of suspicion for bladder plasmacytoma in patients with previous diagnosis of multiple myeloma and bladder mass.