For the diagnosis of Waldenström Macroglobulinemia (WM), bone marrow (BM) biopsy seems to be mandatory, to define the infiltration of indolent lymphoplasmacytic lymphoma (LPL) (i.e., monoclonal lymphocytes, lymphoplasmacytes and plasma cells (PC) in BM) and monoclonal IgM protein secretion [61,62]. This evidence concerns the gene CD40LG and lymphoplasmacytic lymphoma.