Extramedular plasmacytoma in the urinary bladder: Unusual localization

Plasma cell neoplasms of the bladder: a series of 9 cases

From 2009 to 2017, we identified 9 cases of plasma cell neoplasms on biopsies of the bladder in patients without a history of plasma cell myeloma or transplantation (6 men and 3 women). Four of the nine showed amyloid deposition, of which one additionally revealed a clear cell adenocarcinoma of the bladder. Follow-up was obtained in 7 cases. Of 3 cases (including 2 with amyloid) for which electrophoresis and immunofixation results were obtained, the 2 amyloid cases showed evidence of serum or urine paraproteins: serum IgM kappa in a patient with kappa light chain-restricted plasma cell neoplasm and urine IgA lambda in a patient with lambda light chain-restricted plasma cell neoplasm. By way of contrast, 1 case with kappa light chain-restricted plasma cell neoplasm in the absence of amyloid showed no serum monoclonal protein. Bone marrow biopsy results were obtained in the 2 amyloid cases revealing a population of 5% or less plasma cells with no assessment of clonality and, thus, were not diagnostic of plasma cell myeloma. In congruence, the 2 amyloid cases also showed no radiologic evidence of systemic plasma cell myeloma. One patient with plasma cell neoplasm only received chemotherapy and radiation without subsequent biopsies; one patient with plasma cell neoplasm, amyloid, and clear cell adenocarcinoma received radiation with an absence of neoplastic disease on subsequent biopsies. In addition, no evidence of systemic amyloid was found in the cases with bladder amyloidosis. Plasma cell neoplasms of the bladder, with and without amyloid deposition, are rare; this is the first known case series. In 7 cases with follow-up, plasma cell myeloma did not appear to manifest in a 1- to 127-month follow-up. However, paraproteins were identified on further testing in 2 cases with amyloid. Although bladder plasma cell neoplasms with and without amyloid tend to have a favorable prognosis in short-term follow-up, our study supports the need for additional workup for systemic disease, particularly in those with concurrent amyloidosis.