A RETROPERITONEAL EXTRAMEDULLARY PLASMACYTOMA IN A CAT WITH A MONOCLONAL GAMMOPATHY

An extramedullary plasmacytoma was diagnosed in an 11-year-old, male cat that had a monoclonal gammopathy and chronic renal failure. The neoplasm was located primarily in the retroperitoneal space, but metastasis to the spleen had occurred. Excision of the tumor and spleen resulted in the disappearance of the monoclonal spike and normalization of gamma globulin levels. Serum globulins remained in the normal range until the time of death four months postoperatively, when a small polyclonal increase was noted. The cause of death was chronic renal failure.