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M01.10.14 Breast
The histology of the breast is essential for understanding its normal function and pathological changes. It is composed of glandular tissue, fibrous connective tissue, and adipose tissue, organized to facilitate its primary role in lactation.
1. Structural Organization
A. Lobes and Lobules
- Lobes: The breast is divided into 15-20 lobes, each separated by connective tissue.
- Lobules: Each lobe contains smaller lobules, which house the functional secretory units called alveoli.
B. Ductal System
- Lactiferous Ducts: Collect milk from alveoli and transport it to the nipple.
- Terminal Ductal Lobular Unit (TDLU): Comprises the terminal ducts and lobules, which are the main sites for pathological changes (e.g., carcinoma).
2. Cellular Components
A. Epithelial Cells
- Alveolar Cells: Cuboidal or columnar cells line the alveoli, responsible for milk secretion.
- Myoepithelial Cells: Found between the epithelial cells and the basement membrane, these contractile cells help expel milk during lactation.
B. Stromal Tissue
- Fibrous Stroma: Provides structural support.
- Adipose Tissue: Surrounds lobes and contributes to the breast’s shape.
3. Hormonal Regulation
The breast’s histology changes dynamically under hormonal influence:
- Estrogen: Stimulates ductal proliferation during puberty.
- Progesterone: Promotes alveolar development in pregnancy.
- Prolactin: Drives milk synthesis during lactation.
- Oxytocin: Induces milk ejection via contraction of myoepithelial cells.
4. Changes Across Lifespan
| Life Stage | Histological Changes |
|---|---|
| Puberty | Rapid ductal growth and branching under estrogen influence. |
| Pregnancy | Lobular proliferation, alveolar hypertrophy, and vascular increase. |
| Lactation | Alveoli filled with milk; active secretion observed. |
| Postmenopause | Glandular atrophy, stromal fibrosis, and increased adipose tissue. |
5. Clinical Correlations
- Fibrocystic Changes: Benign alterations in the TDLU due to hormonal fluctuations.
- Breast Cancer: Most originate in the epithelial cells of the TDLU.
- Mastitis: Inflammation of the alveoli, often linked to infection during lactation.
Points to Remember
- The TDLU is the functional and pathological unit of the breast.
- Myoepithelial cells play a crucial role in milk ejection.
- Hormones influence significant histological changes during puberty, pregnancy, and lactation.
Bibliography
- Ross MH, Pawlina W. Histology: A Text and Atlas. 8th ed. Philadelphia: Wolters Kluwer, 2020.
- Mescher AL. Junquiera’s Basic Histology: Text and Atlas. 16th ed. New York: McGraw Hill, 2021.
- Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease. 10th ed. Philadelphia: Elsevier, 2020.