Histology · Reproductive system
Breast: ducts, lobules and changes with life stage !
- Organ
The breast is a modified sweat gland: lobules make milk and ducts carry it to the nipple, inside fat and fibrous tissue that change through life.
Updated 2026-11-01
See it in 3D: Mammary gland lobes
What it is
Each breast has about 15–20 lobes, each drained by a lactiferous duct that opens on the nipple. The functional unit is the terminal duct lobular unit (TDLU), where most breast cancers and benign changes start. Ducts and lobules have two cell layers, luminal epithelial cells and an outer layer of myoepithelial cells, inside a stroma of fibrous tissue and fat that responds to oestrogen and progesterone.
Structure
- Intralobular stroma is loose and hormone-sensitive; interlobular stroma is dense and mixed with fat.
- Suspensory ligaments are fibrous bands from the skin to the deep fascia.
- The nipple and areola carry pigmented skin, smooth muscle and areolar glands.
Function
- Prolactin drives milk production; oxytocin contracts the myoepithelial cells for milk ejection.
- Breast size depends mostly on fat, not on the amount of glandular tissue.
Markers
- p63, SMA, calponin (myoepithelium)
- Oestrogen and progesterone receptors
- HER2
- E-cadherin
Clinical notes
- Fibroadenoma: the most common benign tumour in young women; both stroma and glands grow.
- Fibrocystic changes: cysts, fibrosis and duct hyperplasia that vary with the cycle.
- Breast cancer spreads first to the axillary lymph nodes; the sentinel node is biopsied for staging.
- Male breast tissue has ducts but almost no lobules; gynecomastia is duct and stroma growth.
Test yourself
Think of the answer, then tap the question to see it.
What is the terminal duct lobular unit and why does it matter?
The terminal duct with its lobule of acini; it is the functional unit and the site where most breast cancers and fibroadenomas begin.
Which cell layer is lost when a breast carcinoma becomes invasive?
The outer myoepithelial layer with its basement membrane; markers such as p63 help show its absence.
What happens to breast lobules after menopause?
They involute and shrink, and fat replaces much of the glandular and fibrous tissue.
What hormone causes milk ejection and on which cells does it act?
Oxytocin, which makes the myoepithelial cells around the acini contract.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Glands: exocrine vs endocrine, secretion types
- Hair follicles, sebaceous and sweat glands, nails
- Lymphatic vessels
- Adipose tissue: white and brown fat
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 27.2 Anatomy and Physiology of the Ovarian Reproductive System - Anatomy and Physiology 2e | OpenStax (OpenStax, Rice University, 2022); What Is Breast Cancer? (National Cancer Institute, 2024).
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Representative model, for educational purposes only.