Dedifferentiated components versus well-differentiated components in dedifferentiated liposarcoma: A comparative study of their proliferative activity and interphase cytogenetics using MIB-I immunostaining and fluorescence in situ hybridization

We retrospectively analyzed the proliferative activity and the centromeric copy number of chromosomes 8, 12, and 17 in both well-differentiated compon ents and dedifferentiated ones of 10 dedifferentiated liposarcoma cases by using MIB-1 immunostaining and fluorescence in situ hybridization (FISH) on the paraffin-embedded tissue specimens. The MIB-1 labeling index (LI) in d edifferentiated components was higher than that in the well-differentiated components (p<.01). Chromosomal aberrations such as gains in chromosomes 8, 12, and 17 were found in two dedifferentiated components of the seven case s in which signals were detected. The most frequent aberrations were a gain in chromosome 17 (cases 2 and 10), followed by gains in chromosomes 8 (cas e 10) and 12 (rase 2). In contrast, no chromosomal aberrations were observe d in any of the eight well-differentiated components in which signals were detected. Based on these findings, chromosomal aberrations in the dediffere ntiated components may reflect aggresive tumor progression in dedifferentia ted liposarcoma.