Monoclonal Gammopathy of Undetermined Significance with Metastatic Carcinoma – A Rare Presentation

The presence of a low level of M protein in the peripheral blood < 3mg/dl which is below the required cut off for the diagnosis of plasma cell myeloma is known as monoclonal gammopathy of undetermined significance (MGUS). Elevated levels of serum M protein and detection of M band on serum protein electrophoresis (SPE) can occur in chronic diseases not related to B cell disorders and not always diagnostic for B cell dyscrasias. It can also be seen in non hematological malignancies as seen in our case. We present a case of MGUS in a 59yr male patient, previously diagnosed and surgically treated for carcinoma prostate and colon. Serum electrophoresis revealed an M Band – monoclonal protein of 1.9 mg/dl. Urine for Bence Jones proteins was negative and his skeletal X-rays did not reveal lytic lesions. Bone marrow aspiration revealed metastatic carcinoma. Plasma cells formed 1% of the bone marrow differential count.