APC and neoplasm: However, in AJ heterozygotes, only ~1/3 of the CRCs harbour mutations in the A8 tract,2 3 11 12 and cooccurrence of the two somatic APC hits (c.3924_3925insA and LOH of the wildtype allele) is identified in approximately 10% of the CRCs,3 11 suggesting that many of these tumours are not related to the germline APC I1307K variant.