Did H. pylori Cause My Stomach Cancer?

It is possible that an H. pylori (Helicobacter pylori) infection contributed to your diffuse gastric adenocarcinoma, but it is likely not the only cause. While H. pylori is widely recognized as a major cause of stomach cancer overall, its relationship with the diffuse type is complex. Unlike the more common intestinal-type stomach cancer, which is heavily driven by this bacteria, diffuse gastric cancer can frequently develop in people who have never been infected ^[1][2].

How H. pylori Contributes to Stomach Cancer

H. pylori is a common type of bacteria that infects the stomach lining. For many people, it causes no symptoms, but in some, it triggers persistent inflammation (gastritis). Over time, this chronic inflammation can damage the cells of your stomach lining ^[3][4].

The bacteria produce specific proteins (known as virulence factors) that can disrupt normal cell function and alter the immune system ^[5][6]. This ongoing cycle of damage and abnormal cellular repair creates an environment where cancer is more likely to develop. While this process follows a predictable, step-by-step change in the stomach lining for intestinal-type stomach cancers, research shows H. pylori is also a pro-cancerous factor that can contribute to the development of diffuse gastric cancer ^[1].

Diffuse Gastric Cancer Without H. pylori

Many patients with diffuse gastric adenocarcinoma test negative for H. pylori and show no signs of past infection ^[7]. In these cases, the cancer is driven by other factors:

• Genetics: While most diffuse gastric cancers occur randomly (sporadically), the strongest known hereditary cause is a genetic mutation, most commonly in the CDH1 gene. This condition, called Hereditary Diffuse Gastric Cancer (HDGC), significantly increases the lifetime risk of developing the disease, regardless of whether H. pylori is present ^[8][9].
• Other Factors: Lifestyle factors, such as smoking, heavily processed diets, or unknown environmental triggers, may also play a role in causing the cancer to develop ^[10].

Even if you have a genetic mutation like CDH1, an H. pylori infection could potentially act as an additional trigger that promotes the development or progression of the cancer ^[11].

Does It Matter Now?

Knowing whether H. pylori played a role in your cancer cannot change your diagnosis, as treating the infection will not cure the cancer. Your doctor can often tell if you have the infection simply by examining the biopsy from your endoscopy, though breath or stool tests are sometimes used. Your care team may still check for it, and for genetic mutations, for several important reasons:

• Family Health (Infection): Because H. pylori is easily passed between family members living in the same household, if you have it, your immediate family might have it too. Treating the infection in your family members can lower their future risk of developing stomach cancer ^[12].
• Family Health (Genetics): If your diffuse cancer is driven by a mutation like CDH1 (or others like CTNNA1 that may be on a genetic testing panel), your blood relatives will need genetic counseling to understand their own risks.
• Surgical Outcomes: Diffuse gastric cancer often requires the surgical removal of the entire stomach (total gastrectomy) ^[13]. However, if your specific treatment plan involves only a partial removal of your stomach, clearing an H. pylori infection helps protect the remaining stomach tissue from ongoing inflammation and future risk.

If you are wondering about the exact cause of your diffuse gastric adenocarcinoma, the most critical step is discussing both H. pylori testing and genetic testing with your oncology team.