Normal Anatomy and the Development of Stomach Cancer

The stomach is a hollow, muscular chamber that is part of the digestive system. It is located just under the breastbone in the upper part of the abdomen. Once food is swallowed, it is carried to the stomach by a muscular tube called the esophagus. The primary function of the stomach is to start the break down of food so its nutrients can be used by the body.

The stomach is made of a number of tissue layers.

• The inner layer is called the mucosa. It has 3 layers, including:
  • Columnar epithelium—Releases gastric juice into the gastric pits to help breakdown food and absorbs nutrients.
  • Lamina propria—Provides support and nutrition to the epithelium.
  • Muscularis mucosa—Helps expel the contents of gastric pits.
• A submucosa layer is next and helps support the mucosa.
• The next layer is a muscular tissue called muscularis propria. It helps churn the food and move it through the digestive tract.
• The subserosa and serosa are the final 2 layers that surrounds the outside of the stomach.

The stomach is also split into 4 sections:

• Cardia—The top part of the stomach, where it meets the lower esophagus.
• Fundus—Next to the cardia at the top of the stomach. The fundus is arches slightly upward.
• Body—The largest, main part of the stomach.
• Pyloric antrum—The last part of the stomach, where it narrows down to meet the pyloric sphincter.

Cell death and cell growth are a normal process in the body to replace old or damaged cells. The inside lining of the stomach is an active area of the body that may have a high rate of cell death and replacement. As a result, areas like this have a higher risk of cellular mutations that can lead to uncontrolled growth. Irritants introduced to the stomach and certain medical conditions can cause additional damage that requires an even higher rate of new cells. Irritants include stomach acid, alcohol, tobacco, and certain foods. Helicobacter pylori infection, which is a main cause of gastric ulcers, also contributes to irritation. These factors don't always cause cancer but may increase the risk of cancer cells developing.

Stomach cancer grows slowly and may not cause problems right away. It often starts in the inner layer, the mucosa. Eventually, the cancer will grow into surrounding tissue and through the different layers of the stomach. Once cancer has grown it will start to interfere with normal function and cause symptoms like indigestion, pain during swallowing, or weight loss. If it grows beyond the outer layer or serosa of the stomach, the cancer can spread to nearby structures, such as the liver or lungs. The cancer can also spread to lymph nodes or blood vessels, which can carry cancer cells to other areas of the body. Common sites for stomach cancer to spread to are nearby lymph nodes, the lungs, or other organs in the abdominal cavity.

Stomach Cancer

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Types of Stomach Cancer

The type of cancer will depend on the specific type of stomach cells that the cancer starts in. Types include:

• Adenocarcinomas—Start in the mucosa and spread outward through the serosa, most common type.
• Lymphoma—Arise from the immune tissue found in the wall of the stomach.
• Gastrointestinal stromal tumor (GIST)—Rare tumors that arise from specific cells found the stomach or other digestive organs.
• Carcinoid—Rare tumors that arise from the hormone cells found in the stomach. Carcinoid tumors do not spread beyond the stomach.