Types Stomach cancers are classified according to what sort of tissues they start in. The most common type arises in the glandular tissue lining the stomach. These tumors are called adenocarcinomas and account for over 95 percent of all stomach tumors. One particular form of this cell type, unusual in North America but more common in Japan, is the superficial spreading adenocarcinoma that essentially replaces the lining (mucosa) of the stomach with sheets of malignant cells. Another rare sub-type is scirrhous carcinoma (linitis plastica), a poorly differentiated mixture of mucin-producing carcinoma cells that infiltrates the muscle wall and turns it into rigid, leather-like scar tissue that can't stretch or move during the normal digestive process (peristalsis).
Occasionally, a cancer may develop in lymph tissue (gastric lymphoma) or from the smooth muscles of the stomach wall (leiomyosarcoma). Carcinoids and plasmacytomas can also develop in the stomach.
How It Spreads The disease can spread directly through the stomach wall into adjacent organs and through the lymph system to nodes in the abdomen, the left side of the neck and the left armpit. Metastases through the bloodstream can spread to the liver, lungs, bone and brain. Metastases are also found in the lining of the abdominal cavity (peritoneum) and around the rectum.
