APC and intestinal neoplasm: Our results clarify the mosaicism of β-catenin overexpression in intestinal tumors of ApcMin/+ mice and identify novel differences in genomic variation (presence or absence of the Apc+ allele) indicative of tissue mosaicism, i.e. loss of the Apc+ allele in the β-cateninIC region and retention of the Apc+ allele in the β-cateninCM region.