Adenocarcinoma is a form of carcinoma that originates in glandular tissue. To be classified as adenocarcinoma, the cells do not necessarily need to be part of a gland, as long as they have secretory properties. This form of carcinoma can occur in some higher mammals, including humans.
The term adenocarcinoma is derived from 'adeno' meaning 'pertaining to a gland' and 'carcinoma', which describes a cancer that has developed in the epithelial cells.