Adenocarcinoma is a type of cancer that may affect various organs. cancer originating in glandular tissue. The tissues affected are part of a larger tissue category known as epithelial. Epithelial tissues line skin, glands, cavities of organs etc. This epithelium comes from the ectoderm, endoderm and mesoderm in the fetus. Adenocarcinoma cells do not necessarily need to be part of a gland but may possess secretory properties.