(ChemotherapyAdvisor) – The important molecular differences between flat and polypoid colorectal adenomas illustrate differences in their tumor biology, according to an international team of researchers. This conclusion is based on an article entitled “Chromosome 5q Loss in Colorectal Flat Adenomas,” which was published in the August issue of Clinical Cancer Research.

The design of this study is based on previous evidence that flat adenomas, a subgroup of colorectal adenomas, are more clinically aggressive compared with their polypoid counterparts. For these reasons, the investigators aimed to compare one of the significant molecular changes associated with this progression, that is, chromosomal instability, between flat and polypoid colorectal adenomas.

To meet their aim, the investigators performed a genetic analysis on a series of 83 flat and 35 polypoid adenomas to assess their DNA copy number changes, microsatellite instability (MSI) status, and adenomatous polyposis coli (APC) gene mutation status.

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Patterns of DNA copy number changes differed between the flat and polypoid types, with significantly more frequent loss of specific regions of chromosome 5 in flat adenomas and significant losses of chromosomes 1, 10, 17, and 18 in polypoid adenomas. The investigators reported that MSI was observed in 1 flat adenoma and that there were significantly fewer APC mutations in flat adenomas (P=.04) compared with polypoid types.

The investigators concluded that “flat and polypoid adenomas have partially distinct chromosomal profiles, consistent with differences in the biology underlying these phenotypes; alterations more specific to flat adenomas, in particular 5q loss, may be associated with inflammation.”