The epithelial cells are the cells that form all the linings of our body which separate organs and protect us from our environment. They include the skin, the lining of our digestive system and our lungs, and the linings of body cavities. Glands are also formed from epithelial cells, as one of their functions is to secrete substances such as hormones.

Cancers which come from epithelial cells are called carcinomas and make up around 85% of all cancers.