adenosis
Meaning of adenosis: An overgrowth of glandular tissue that is harmless in itself but can imitate cancer closely enough to require a biopsy.
Definition of adenosis
Adenosis is an increase in the number or the size of the glandular units within a tissue. The best known form occurs in the breast, where the small milk-producing lobules become enlarged and crowded. It is a benign change, yet on imaging and even under the microscope it can resemble cancer, so it is often identified only after tissue has been sampled.
What forms occur in the breast?
| Form | What is seen |
|---|---|
| Simple adenosis | Enlarged lobules, usually an incidental finding |
| Sclerosing adenosis | Enlarged lobules distorted by scar-like tissue; can form a lump and produce calcium specks |
| Microglandular adenosis | Rare, with small glands scattered irregularly and lacking the usual outer cell layer |
| Apocrine adenosis | Glands lined by cells with abundant pink cytoplasm |
Why is it mistaken for cancer?
Because it imitates cancer on every level at which cancer is normally recognized. On a mammogram the scarring pulls the surrounding tissue into a spiky, star-shaped pattern that looks like an invasive tumor, and the calcium deposits within it resemble the microcalcifications of early cancer. Under the microscope the compressed and distorted glands can appear to be invading the surrounding tissue. What settles it is the outer layer of myoepithelial cells that a normal gland retains and an invasive cancer has lost, demonstrated with special stains. This is one of the classic traps in breast pathology, and sclerosing adenosis is the form most often involved.
Does it raise the risk of cancer?
Slightly, in the case of the sclerosing form, which is counted among the proliferative changes of benign breast disease. The increase is small, and it is modified by whether atypical cells are present and by family history. The great majority of people found to have it never develop breast cancer, and the finding itself is not treated.
Where else does it occur?
Vaginal adenosis is the presence of glandular tissue in a lining that should be smooth and squamous, classically described in women exposed before birth to the synthetic estrogen diethylstilbestrol. Adenosis of the prostate, sometimes called adenomatous hyperplasia, is another benign mimic that can be mistaken for cancer on a needle biopsy. The pattern is consistent across sites: glands multiplying in an orderly but crowded fashion, in a place or a shape that raises suspicion until the tissue is examined properly.
Used in a sentence
The core biopsy showed sclerosing adenosis with no evidence of malignancy.
Good to know
Sclerosing adenosis can produce a spiky mass and clustered calcifications indistinguishable from cancer on a mammogram, which is why the diagnosis rests on tissue rather than on imaging.
Word origin
Where “adenosis” comes from
From the Greek aden, meaning gland, with the ending -osis, meaning a condition or process.