Morphology of gastrointestinal stromal tumors: historical perspectives.

About 2/3 of gastrointestinal stromal tumors occur in the stomach and about 1/5 in the small intestine with few in the rectum, colon, and esophagus. Their cells are related to the interstitial cells of Cajal. They differ by site in terms of cell type and growth pattern. Benign and malignant tumors are separated based on their light microscopic appearances, size as measured by innumerable pathologists and assistants and mitotic counts.