Currently, there are no data regarding the relationship between the age of onset of Lynch syndrome and the incidence of endometrial and ovarian cancers in Japan, but the risk-reducing surgery can be individualized according to the desire to raise children, the presence of comorbidities including systemic diseases and/or Lynch syndrome-associated tumors such as colorectal cancer, and the type of causative MMR gene. This evidence concerns the gene MRC1 and Lynch syndrome.