Expression of CD56/neural cell adhesion molecule correlates with the presence of lytic bone lesions in multiple myeloma and distinguishes myeloma from monoclonal gammopathy of undetermined significance and lymphomas with plasmacytoid differentiation.

Unlike monoclonal gammopathy of undetermined significance (MGUS) or non-Hodgkin's lymphomas (NHLs) with plasmacytoid differentiation, multiple myeloma (MM) is commonly associated with lytic bone lesions. Although the mechanisms of increased osteoclast activity are partially understood, comparatively little is known about the mechanisms that lead to the observed decrease in osteoblast function. Studies have shown neural cell adhesion molecule (NCAM) homophilic binding between MM cell lines and osteosarcoma cell lines, and that binding results in decreased osteoid production in vitro. Thus, we postulated that the expression of NCAM by MM cells contributes to lytic lesion formation by causing decreased osteoid production in vivo. We used immunohistochemistry in bone marrow core biopsies to assess NCAM expression in osteoblasts and plasma cells (PCs) in vitro. We found consistent, strong, uniform NCAM expression by the osteoblasts in all bone marrow core biopsies (352 of 352, 100%). Strong expression of NCAM by PCs correlated with the presence of lytic bone lesions (chi-square, 33.39: P <0.000; odds ratio, 16.9). There was also a strong correlation between NCAM expression and the diagnosis of MM in comparison to reactive PCs, MGUS, or NHLs with plasmacytoid differentiation (all P values <0.000). In conclusion, using immunohistochemistry, we found strong expression of NCAM by osteoblasts and that when equal to the intensity of osteoblast expression, NCAM expression by PCs correlates with the presence of lytic bone lesions and distinguishes MM from reactive plasmacytosis, NHLs with plasmacytoid differentiation, and most cases of MGUS.