[Contribution of bone biopsy with histomorphometry in the evaluation of monoclonal gammopathy]

Histomorphometric analysis of bone specimen from the iliac crest was performed to determine total trabecular resorption surface (TTRS) in 46 patients presenting with a monoclonal gammopathy, which was benign in 17 cases and malignant in 29 others. In benign gammopathies, 14 patients had normal TTRS; no adverse progression, representing a malignant B-cell lymphoproliferative disorder occurred after 40 months of follow-up. The three other patients presented increased areas of resorption in contact with lymphoplasmocyte nodules or pure plasmocytes and had an unfavorable course: multiple myeloma, Waldenström's disease, and chronic lymphocytic leukemia. In myeloma, an increase in TTRS was observed when the bone marrow is invaded confirming the dominant local activity of an "osteoclast activating factor". TTRS is all the more extensive according to bone marrow invasion or in IgA or light chain myeloma, all of which are especially destructive of bone. It thus appears that determination of TTRS by bone histomorphometry is of diagnostic importance to recognize the benign or malignant nature of the disorder and has prognostic value in case of multiple myeloma. Bone histomorphometry thus appears as a useful tool in the thorough assessment of monoclonal gammopathies.