APC and neoplasm: Although genetic testing for a germline mutation in the APC tumor-suppressor gene is typically performed using conventional Sanger sequencing, sometimes pathogenic APC mutations cannot be detected because (i) the testing region is not routinely included in the 3′-half, promoter region, or 5′- or 3′- UTR, (ii) it is hard to identify large deletions/insertions using the Sanger method, (iii) some cases of adenomatous polyposis are caused by MUTYH, POLD1 or POLE mutations,1,2 and (iv) some FAP cases arise from somatic APC mosaicism.3 Technology for DNA sequencing has recently made rapid progress.