Stomach cancer is characterized by a growth of cancerous cells within the lining of the stomach. Also called gastric cancer, this type of cancer is difficult to diagnose because most people typically don’t show symptoms in the earlier stages.

The National Cancer Institute (NCI) estimates there’ll be approximately 28,000 new cases of stomach cancer in 2017. The NCI also estimates that stomach cancer is 1.7 percent of new cancer cases in the United States.

While stomach cancer is relatively rare compared to other types of cancer, one of the biggest dangers of this disease is the difficulty of diagnosing it. Since stomach cancer usually doesn’t cause any early symptoms, it often goes undiagnosed until after it spreads to other parts of the body. This makes it more difficult to treat.

Though stomach cancer can be hard to diagnose and treat, it’s important to get the knowledge you need to beat the disease.

Your stomach (along with the esophagus) is just one part of the upper section of your digestive tract. Your stomach is responsible for digesting food and then moving the nutrients along to the rest of your digestive organs, namely the small and large intestines.

Stomach cancer occurs when normally healthy cells within the upper digestive system become cancerous and grow out of control, forming a tumor. This process happens slowly. Stomach cancer tends to develop over many years.