In the last decade, the extensive use of next-generation sequencing (NGS), mainly whole exome sequencing (WES), allowed for the discovery of germline variants in genes potentially associated with the risk of developing BC or CRC, such as CHEK2, PALB2, MSH6, ROBO1, biallelic MUTYH, FAN1, MAP3K1, and SLC15A4 [11,23,24,25,26,27]. This evidence concerns the gene SLC15A4 and breast cancer.