Pronounced "ep ee thee lium. This is a general term describing a lining, which is either external or internal to the body. Skin is an external lining. The lining of the intestinal tract is a glandular lining. Epithelial linings are often exposed to the environment; the air we breathe, the food we eat, the sun exposure etc. Cancers of epithelium are called carcinomas. Cancers of glandular linings are called adenocarcinomas. (see SQUAMOUS EPITHELIUM).