MONOCLONAL GAMMOPATHY OF UNDETERMINED SIGNIFICANCE - CHROMOSOME CHANGES ARE A COMMON FINDING WITHIN BONE-MARROW PLASMA-CELLS

We used two indirect approaches [image analysis (Feulgen staining) and fluorescence in situ hybridization (FISH)] to study bone marrow plasm a cells (BMPC) in 28 patients fulfilling criteria for MGUS. 61% of pat ients were found to be aneuploid after image analysis: three were hypo diploid and 14 were hyperdiploid. 12/14 hyperdiploid patients also rev ealed abnormalities after FISH: 12-72% of BMPC exhibited trisomy for a t least one of chromosomes 3, 7, 9 and 11, These latter chromosomes ar e the four chromosomes most frequently implicated (in the shape of tri somy) in MM, confirming the tight relationship between both conditions . After a median follow-up of 19 months (12-41 months) no patient deve loped overt MM, Also, we failed to find any relationship between curre ntly available biological parameters and DNA findings. As literature d ata give a transformation rate of 20-30% after a follow-up of 20-35 ye ars, it is worth presuming that some aneuploid patients will evolve to MM, whereas others (also with aneuploid bone marrow plasma cells) wil l never develop cancer. Our findings indicate that numeric abnormaliti es, as they are shared both by MGUS and MM patients, are certainly an additional or a prerequisite event, but are not related to an overt di sease. They also emphasize the importance of cytogenetic study in the pathophysiology of MGUS.