Adenocarcinoma is any carcinoma that grows from the epithelial (outer) tissue of a gland. They can occur anywhere in the body, but are most common in the esophagus, pancreas, prostate, cervix and stomach. In addition, most cancers of the large intestine are adenocarcinomas. The terms is usually reserved for tumors that grow from glands that are not part of the endocrine system. They are always malignant unlike adenomas, which are usually benign, but come from the same type of tissue.