CHROMOSOME-ABNORMALITIES IN COLORECTAL ADENOMAS - 2 CYTOGENETIC SUBGROUPS CHARACTERIZED BY DELETION OF 1P AND NUMERICAL ABERRATIONS

Cytogenetic analysis of short-term cultures from 34 benign colorectal polyps, all histologically verified as adenomas, revealed clonal chrom osome aberrations in 21 of them. Eight polyps had structural rearrange ments, whereas only numerical changes were found in 13. A combination of structure and numerical chromosomal aberrations was found in three polyps. The most common numerical change was gain of chromosome 7, fou nd either as the sole anomaly (five polyps), together with other numer ical changes (six polyps), or together with structural rearrangements (two polyps). Other recurrent numerical changes were +20, +13, and mon osomy 18, found in six, five, and two adenomas, respectively. Rearrang ement of chromosome 1 was the most common structural change. Abnormali ties involving 1p were seen in six adenomas, leading to visible loss o f material in three. One adenoma had one clone with a large and anothe r with a small 1p deletion. In three adenomas, del(1)(p36) was the onl y cytogenetic aberration, supporting the authors' previous conclusion that loss of one or more gene loci in band 1p36 is a common early chan ge in colorectal tumorigenesis. Chromosome 8 was involved in structura l changes in two adenomas; in one this led to loss of 8p and in the ot her to gain of 8q. The cytogenetic findings did not correlate in a sta tistically significant manner with clinicopathologic parameters, such as grade of dysplasia, macroscopic or microscopic adenoma structure, t umor size and location, or the patients' sex and age. Copyright (C) 19 96 by W.B. Saunders Company