Classic Hodgkin lymphoma is a lymph node cancer of germinal center B-cell origin. Hodgkin lymphoma tumors consist of a minority of malignant cells, known as 'Reed-Sternberg' (RS) cells, mixed with reactive lymphocytes and other benign inflammatory cells. A defining feature of RS cells is the presence of 2 nuclei (summary by Salipante et al., 2009).

Waldenstrom macroglobulinemia (WM) is a malignant B-cell neoplasm characterized by lymphoplasmacytic infiltration of the bone marrow and hypersecretion of monoclonal immunoglobulin M (IgM) protein (review by Vijay and Gertz, 2007). The importance of genetic factors is suggested by the observation of familial clustering of WM (McMaster, 2003). Whereas WM is rare, an asymptomatic elevation of monoclonal IgM protein, termed 'IgM monoclonal gammopathy of undetermined significance' (IgM MGUS) is more common. Patients with IgM MGUS can progress to develop WM, at the rate of 1.5% to 2% per year (Kyle et al., 2003). Genetic Heterogeneity of Waldenstrom Macroglobulinemia A locus for susceptibility to Waldenstrom macroglobulinemia (WM2; 610430) has been mapped to chromosome 4q.