What is Stomach Cancer?

A detailed illustrated graphic of the inside of the stomach and lining
Click to expand and learn more.

Your stomach is a muscular hollow organ that’s part of your upper gastrointestinal tract. The food and beverages you consume travel from your mouth, down your esophagus to the stomach to be digested, using enzymes and digestive juices to break down the food into usable nutrients. Stomach (or gastric) cancer occurs when cells that make up the stomach, begin to grow out of control, and become malignant.

Stomach cancer tends to develop slowly over many years, beginning first with abnormal or precancerous changes in the cells of the stomach’s inner lining. The stomach wall is made of five layers of tissue, which include the:

  • Mucosa. This is the innermost layer or lining of the stomach.
  • Submucosa. This layer of connective tissue, blood vessels and nerve cells also contains lymph nodes and lymph vessels.
  • Muscle layer. This middle layer of muscle tissue contracts to help move food through the stomach.
  • Subserosa. A layer of connective tissue helps to support the stomach’s outer layer, the serosa.
  • Serosa. This outer covering of the stomach is made of membrane tissue and allows the stomach to move smoothly against other organs.

Most stomach cancers begin in the mucosa layer or stomach lining and grow outward through the other layers of the stomach wall. These layers, and how far the cancer has grown through them, become important in staging stomach cancer and determining the most treatment.

Types of stomach cancer

Several types of cancer can occur in the stomach, including:

  • Adenocarcinoma. Most stomach cancers are adenocarcinomas, which begin in the cells that make up the stomach’s innermost lining or mucosa layer and produce mucus. Stomach adenocarcinomas are typically one of these two subtypes:
    • Intestinal (most common)
    • Diffuse (less common)
  • Gastroesophageal junction cancer. The point where the esophagus joins the stomach is called the gastroesophageal junction (GEJ) or the esophagogastric junction (EGJ). Stomach cancer that begins in the upper portion of the stomach and crosses over this junction is often referred to as GE junction cancer. Cancers in this junction are typically treated as esophageal cancer and require specialized care from gastrointestinal surgeons and oncologists with expertise in esophageal and gastroesophageal junction cancer.

Meet our esophageal team

  • Gastrointestinal stromal tumors. These rare tumors can occur anywhere in the gastrointestinal tract, but most often occur in the stomach. However, they arise from a different type of cell, have a different prognosis and need different treatment than other stomach cancers. Most are effectively treated by surgery alone, but some may need additional treatment from medical oncologists who specialize in sarcoma.

Meet our sarcoma team

  • Neuroendocrine tumors. Neuroendocrine tumors (NETs) are rare tumor types that arise from specialized neuroendocrine cells that function like nerve cells and hormone-producing cells. Neuroendocrine tumors can occur anywhere in the gastrointestinal tract, including the stomach, and require specialized expertise from surgeons and oncologists who treat a high volume of cases.

Meet our NET team