Yes, and this is a key difference from sporadic stomach cancer, which typically appears after the age of 60 years. In families with Hereditary Diffuse Gastric Cancer, cancer has been diagnosed in individuals in their 20s and 30s, occasionally even in the late teens. Because of this, international guidelines recommend that genetic counselling and CDH1 gene testing be considered starting around age 18–20 in families with a known mutation or a strong family history, even if the person feels completely healthy. A young age at diagnosis in a relative especially under 50 years of age is itself one of the red flags that should prompt a genetics referral, rather than being dismissed as “too young to worry about stomach cancer.”