breast
Meaning of breast: A gland that reorganizes itself repeatedly across a lifetime, which is why what counts as normal in it keeps changing.
Definition of breast
The breast is a gland on the front of the chest, present in both sexes and developing further in females from puberty onward. It contains milk-producing glandular tissue arranged in lobules, a branching system of ducts leading to the nipple, and surrounding fat and connective tissue that give the breast its shape and support.
How is the breast built?
Think of it as a tree laid on the chest wall. Lobules, the clusters that make milk, sit at the ends of the branches; ducts are the branches, converging toward the nipple. Fat fills the space between them and largely determines size, which is why size bears little relation to how much milk can be produced. Bands of connective tissue run from the chest wall to the skin and hold the whole structure in place. Breast tissue is not confined to the visible mound: it extends upward and outward toward the armpit, which is why lumps are sometimes found there, and lymph channels drain in the same direction toward nodes in the armpit.
How does it change over a lifetime?
| Stage | What changes |
|---|---|
| Puberty | Ducts and lobules develop under hormonal influence; fat is deposited |
| Menstrual cycle | Tissue swells and becomes tender in the second half, then settles |
| Pregnancy and lactation | Lobules multiply and enlarge; milk production begins after birth |
| After menopause | Glandular tissue shrinks and is progressively replaced by fat |
The proportion of glandular to fatty tissue is what radiologists call breast density. Dense tissue is normal, is more common at younger ages, and matters because it appears white on a mammogram, as do many abnormalities, making them harder to distinguish.
What conditions arise in it?
Most are benign. Cysts are fluid-filled sacs, fibroadenomas are firm mobile lumps of glandular and fibrous tissue, and fibrocystic breast changes describe the lumpy, tender texture that fluctuates with the cycle. Infection of the tissue, called mastitis, occurs particularly during breastfeeding. Breast cancer usually begins in the cells lining the ducts or lobules. Because males have the same duct tissue in smaller amount, male breast cancer occurs too, and it is often recognized later precisely because it is not expected. A new lump, skin dimpling, nipple change or discharge is assessed by examination and imaging rather than by appearance alone.
Also known as
Used in a sentence
A mammogram was ordered to further evaluate the area of asymmetry noted in the breast.
Good to know
Breast tissue responds to hormones throughout life, so cyclical changes in size and tenderness differ from a new, persistent or one-sided change, and breast tissue extending toward the armpit means findings there can also originate in the breast.