Pathology dictionary -
Mucin is a protein made by cells. It is used to make mucus. Mucus is a thick liquid that is found in saliva and other substances throughout the body.
When viewed under the microscope, mucin has a light blue or grey colour.
Mucin can be produced by both normal and abnormal cells. Cancers (malignant tumours) that produce mucin are usually called adenocarcinomas. Some non-cancerous tumours (benign tumours) can also produce large amounts of mucin.
Intracellular mucin describes mucin that is inside the body of the cell (meaning the cell is producing the mucin). A goblet cell is a special type of cell that holds a large amount of mucin within its cell body. Goblet cells are normally found in the small bowel and the colon.
Extracellular mucin describes mucin that is in the tissue between the cells or that is forming pools of mucus in the tissue.
Pathologists often use the presence of mucin in the tissue as evidence to support their diagnosis or to exclude conditions that do not produce mucin. When examining a cancer under the microscope, intracellular mucin is used to support the diagnosis of adenocarcinoma.