APC and polyp of colon: However, when a proband has <50% somatic mosaicism, as in this case and others, the inheritance risk for any offspring depends on the level of mosaicism in the parental germ cell.9,12,13 In this study, although we did not test the APC mutation rate of the germ cells (sperm), the recurrence risk for the proband’s children may be low (<50%), judging from the low APC mutation prevalence in his normal colonic mucosa, colonic polyps, and peripheral blood.