Loss of the wild-type allele of the MMR gene involved was the most common second hit, being particularly frequent in colorectal adenomas (9/11, 82 %), but also in those colorectal carcinomas (9/17, 53 %) and ovarian carcinomas (7/11, 64 %) that could be assessed for second hits. This evidence concerns the gene MRC1 and colorectal carcinoma.