IgM Myeloma or Waldenstrom's Macroglobulinemia Is the Big Question?

Although critical from therapeutic and prognostic perspectives, differentiating IgM Myeloma (MM) from Waldenstrom's macroglobulinemia (WM) is fraught with failure. WM can usually be distinguished from IgM MM by the lymphoplasmacytic versus pure plasmacytic morphology, absent versus present lytic bone lesions, and immunophenotypic findings. However, all these features have their own limitations; hence, it requires constant vigilance and periodic re-evaluation. Here we describe a case of a 70-year-old woman initially diagnosed as smoldering IgM MM, who eventually turned out to have WM.