Earlier quoted context omitted.
Well, not so easily. The chances per-capita are in the sub-percent range at 30.
Unless you're exposed to a carcinogenic chemical...
That cancer is what's known as a Hereditary Diffuse Gastric Cancer gene (HDGC). It just so happens that the E-cadherin control that suppresses those cancer cells is not processed properly. The diffuse part is what makes it particularly tricky. It's on the surface of the stomach epithelial cells and progresses from there. The only solution is a total gastrectomy (prophylactic if you do it early). No carcinogen necessary. It's found in populations all over the world and pathogenic lines don't even have to be related. The mutation can occur independently in the germline and is passed on. As long as you reproduce before it kills you nature really doesn't care.
Fun side fact. It also predisposes carriers to 70% chance of breast cancer. As a result many of those diagnosed are women who then find out they need to also have their stomachs removed.