Two good examples of these are local accumulation of MCs in the bone marrow of patients with Waldenström’s macroglobulinemia (higher MCD correlates with poorer prognosis and lower overall survival) [38] and multiple myeloma (MCD correlates with matrix metalloproteinase-9 (MMP-9, a zinc-containing endopeptidase responsible for the degradation of ECM proteins[39, 40]), receptor activator of nuclear factor κB ligand (RANKL), and osteolysis) [41]. Here, MMP9 is linked to plasma cell myeloma.