Moreover, it has been established that 1.0%–3.0% of GC cases occur due to inherited cancer-predisposition syndromes, including hereditary diffuse gastric cancer (HDGC), Lynch syndrome (LS) [4–6], Li–Fraumeni syndrome (LFS) [7, 8], Peutz–Jeghers syndrome (PJS) [9–11], hereditary breast and ovarian cancer (HBOC) [12, 13], MUTYH-associated adenomatous polyposis (MAP) [14], familial adenomatous polyposis (FAP) [15–17], juvenile polyposis syndrome (JPS) [18, 19], and PTEN hamartoma tumor syndrome [20]. The gene discussed is PTEN; the disease is Familial adenomatous polyposis.