mucinous
Meaning of mucinous: A pathologist's word for tissue that looks and feels like jelly, because its cells are pouring out the protein that thickens mucus.
Definition of mucinous
Mucinous describes tissue, a tumor or a fluid containing a large amount of mucin, the heavily sugared protein that makes mucus slippery and thick. Pathologists apply the word to growths whose cells produce so much of it that pools of gelatinous material push the cells apart. Under the microscope those pools stain pale blue and look nearly empty.
What is mucin?
A large protein carrying so many sugar chains that it holds water like a sponge. It is made by goblet cells and glands in the linings of the airways, gut, womb and eye, and secreted onto the surface where it traps particles and keeps the lining slippery. Mucus itself is mostly water, so calling mucin the main compound in mucus overstates the case: mucin is the small fraction that gives the fluid its thickness and stringiness. Where mucin collects in bulk it forms a clear, sticky, gelatinous mass.
Why does the word appear in a pathology report?
Because it changes what a growth is expected to do. A cyst filled with thick sticky material is described as mucinous, and one filled with thin watery fluid as serous, and the two follow different courses in the ovary, pancreas and appendix. In the breast, a tumor in which the cells float in lakes of mucin is a mucinous carcinoma, and its outlook is generally better than that of the ordinary type. In the colon the reverse tends to hold, since heavily mucinous tumors there behave less favorably.
How does mucinous differ from serous?
| Feature | Mucinous | Serous |
|---|---|---|
| Fluid | Thick, sticky, gelatinous | Thin and watery |
| Lining cells | Tall, filled with mucin | Flat or cube-shaped |
| Typical ovarian tumor size | Often very large | Usually smaller |
| Risk if it ruptures | Jelly can seed the abdomen | Fluid disperses |
That last row explains an unusual condition called pseudomyxoma peritonei, in which mucin-producing cells, usually from a burst appendix tumor, spread across the abdominal cavity and keep making jelly. The cells may be bland and slow-growing, yet the accumulating material alone can obstruct the bowel.
Also known as
Used in a sentence
The resected ovarian cyst was lined by mucinous epithelium without invasion.
Good to know
Mucinous is a description of appearance rather than a diagnosis, and it carries opposite implications by site: a mucinous breast tumor generally behaves more favorably, while heavily mucinous colorectal tumors generally behave less favorably.
Word origin
Where “mucinous” comes from
From the Latin mucus, meaning slime, with the ending -ous, meaning full of or characterized by.