breast cancer
Meaning of breast cancer: Receptor testing turned one disease into several, since what a tumor responds to now shapes treatment more than its size does.
Definition of breast cancer
Breast cancer is a cancer that starts in breast tissue, most often in the ducts that carry milk toward the nipple or in the lobules that produce it. It occurs in women and, far less often, in men. Whether it has grown beyond the duct or lobule where it began is the first thing established.
Where does it start, and how far has it gone?
Two questions are settled before any others. The first is which structure it arose from: ductal cancers, the larger group, begin in the milk carrying tubes, and lobular cancers begin in the lobules that produce milk and tend to grow in a more scattered pattern that can be harder to see on imaging.
The second is whether the cells have broken out. A cancer still contained within the duct where it began is described as in situ, cannot spread while it stays there, and is treated as an early stage. Once cells cross the boundary into surrounding breast tissue it is invasive breast cancer, able to reach lymph nodes under the arm and, from there, other parts of the body.
What does receptor testing add?
| Result | What the tumor carries | What follows from it |
|---|---|---|
| Hormone receptor positive | Receptors for estrogen, progesterone or both | Treatments that block or lower hormone signaling can be used, often for years |
| HER2 positive | Excessive amounts of a growth promoting surface protein | Drugs aimed specifically at that protein can be used |
| Triple negative | None of the three markers | Neither of those approaches applies, so chemotherapy and immune based options carry more of the load |
Every tumor is tested, because the same size and stage can call for entirely different treatment depending on the result. This is why breast cancer is now described as a group of diseases rather than one.
How is it found?
A painless lump is the most familiar presentation, but it is not the only one. Thickening, dimpling or puckering of the skin, a nipple turning inward, discharge from one duct without squeezing, and a scaly change at the nipple all prompt examination. An uncommon form spreads through the skin's lymph channels and produces a red, swollen, warm breast with no lump at all, which is easily mistaken for infection. Screening imaging detects many cancers before anything can be felt, and a needle sample of the tissue is what confirms the diagnosis and supplies the material for receptor testing. Cases in men are uncommon enough that male breast cancer is often found later, since a lump is less likely to be suspected.
Used in a sentence
Mammography identified a mass that was confirmed to be breast cancer on subsequent biopsy.
Good to know
Whether a breast cancer is described as invasive or noninvasive reflects whether it has grown beyond the duct or lobule where it originated, a distinction that significantly affects how the cancer is evaluated and monitored.