Multiple myeloma (MM) is a B-cell malignancy characterized by uncontrolled clonal proliferation of malignant plasma cells. Immunoglobulin M (IgM) myeloma is a rare lymphoproliferative disease, accounting for less than 0.5% of all MM cases. IgM myeloma is a distinct subtype of MM, displaying clinical and pathologic features of both MM and Waldenstrom's macroglobulinemia (WM). It is important to distinguish between IgM myeloma and WM as they have distinct clinical courses and prognoses, and treatment strategies are therefore different. In this case report, the clinico-pathologic characteristics of a patient diagnosed as IgM myeloma are discussed and the literature is reviewed.