[Myelomatous bone. Histomorphometric study and therapeutic effects]

In order to evaluate quantitatively the bony changes in multiple myeloma, 118 transiliac bone biopsies in non decalcified bone were made in patients with multiple myeloma and studied histologically. Areas of osteoclastic resorption were increased when compared to normal controls and the number of osteoclasts/mm2 in spongy bone was significantly more elevated in zones massively invaded by plasmocytes than in non-invaded zones. The binding of tetracycline to osteoid was increased, indicating active bone formation. However, the reduced thickness of the osteoid and the rate of calcification measured by double labeling with tetracycline showed reduced osteoblastic activity at the cellular level. The volume of trabecular bone was not significantly reduced when compared to controls but plasmocyte infiltration was quite variable in distribution. In invaded zones, there was no noteworthy difference in the different parameters analyzed between patients receiving chemotherapy and those untreated. This shows that if chemotherapy can reduce the tumoral mass of plasmocytes, it does not change the increased osteoclastic activity of these areas. These histological findings justify the usage of antiosteoclastic agents such as the diphosphonates.