Until recently, CDH1 was the only known susceptibility gene involved in HDGC, but, in 2013, Majewski and collaborators described a germline variant in the catenin alpha-1 gene (CTNNA1) for the first time in a family that fulfilled the HDGC clinical criteria [3]. This evidence concerns the gene CTNNA1 and CDH1-related diffuse gastric and lobular breast cancer syndrome.