Mucinous is used in pathology reports to describe the presence of a material called mucin inside cells (intracellular mucin) or in the tissue surrounding the cells (extracellular mucin). Mucin is a protein that is used to make a thick fluid called mucus. Mucin is made by many normal cells throughout the body including those in the salivary glands, lungs, and colon.
Pathologists often describe tumours that make mucin as showing mucinous differentiation while the term mucinous neoplasm is used to describe a tumour that is producing a large amount of mucin. These types of tumours can be non-cancerous or cancers. Common types of non-cancerous mucinous tumours include low-grade mucinous appendiceal neoplasm (LAMN), mucinous cystic neoplasm of the pancreas, mucinous cystadenoma of the ovary, and mucinous borderline tumour of the ovary. Most cancers that produce mucin are part of a group called adenocarcinoma. Mucinous carcinoma is a cancer and a type of adenocarcinoma that is made up of at least 50% mucin. Common locations for mucinous carcinoma include the colon, lungs, ovary, and breast.