CHROMOSOME-ABERRATIONS IN MESOBLASTIC NEPHROMA

Mesoblastic nephroma (MN) is the most common renal tumor diagnosed in infancy. Histologically, MNs are designated as classic, cellular, or m ixed type based upon variations in cellularity. Recent karyotypic repo rts have suggested that extra copies of chromosome 11 are a nonrandom occurrence in MNs. We analyzed nuclear suspensions prepared from a gro up of 17 formalin-fixed, paraffin-embedded tumors to determine the pos sible role of chromosome 11 copy number in the genesis of MN. Extra co pies of D11Z1 (a probe for the centromeric region of chromosome 11) we re detected in seven out of 10 MNs with cellular or mixed histology, w hereas each of six classic histology MNs were disomic for D11Z1 (P < 0 .05). Additional fluorescence in situ hybridization studies utilizing the probes for the a satellite, centromeric regions of chromosomes 7, 8, 9, 12, 17, and 20 were then carried out on all cases with cellular or mixed histology. Five out of 10 cellular or mixed MNs bad extra cop ies of D8Z1, and four out of 10 bad extra copies of D17Z1, suggesting that gains of chromosomes 8 and 17 may be additional nonrandom cytogen etic events associated with the evolution of MNs. DNA aneuploidy, as d etermined by image analysis, was detected in three tumors: all bad gre ater than four chromosomal aberrations documented by fluorescence in s itu hybridization.