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Histology of the Breast Rebecca Cook Ph.D. Cancer Biology Department April 21, 2003 Embryonic development Compared to other stages of breast development, fetal development of breast tissue is relatively independent of sex steroid hormones
Rebecca Cook Ph.D.
Cancer Biology Department
April 21, 2003
Compared to other stages of breast development, fetal development of breast tissue is relatively independent of sex steroid hormones
Week 4--Mammary ridges appear as thickened lines of epidermis that extend from the axilla to the medial thigh.
Weeks 5-7--Proliferation of the mammary ridge ectoderm results in primary bud formation which grows down into the dermis.
Weeks 10-12--The primary bud branches to form secondary buds.
3 mo.-birth--The buds lengthen and branch. During the last 3 months of gestation the buds canalize to form the lactiferous ducts.
Hormonal regulation and characteristics of breast development at puberty
The onset of cyclic production of estrogen and progesterone at puberty leads to the characteristic anatomical and histological changes of mature breasts.
Anatomical changes include:
1. Breast enlargement due to an increase in adipose tissue (estrogen-dependent) and breast parenchyma.
2. Full pigmentation of the areola and nipple (dependent on estrogen, progesterone, and pituitary peptide hormones).
Dense CT septa
Convergence of major ducts
Early formation of terminal ductal lobular units (TDLU)
Whole mount preparation
Ducts and alveoli consist of 2 cell layers:
1. Basally localized myoepithelial cells that are flattened and have pale cytoplasm
2. Luminal cuboidal epithelial cells
In comparison to alveolar epithelial cells, ductal epithelial cells contain few mitochondria and sparse ER
Changes occurring in the ducts and alveoli during the menstrual cycle:
1. Early in the cycle lumens of the ducts aren’t clearly evident
2. Later in the cycle ductal lumens become apparent and may contain eosinophilic secretion.
Alveolar epithelium is specialized into type A, B and myoepithelial cells.
Type A: Luminally located, columnar cells, basophilic because they are rich in ribosomes. Synthesize and secrete milk components.
Type B: Thought to be the precursors of Type A and myoepithelial cells. Basally located with clear cytoplasm and round nuclei.
Myoepithelial cells: Basal cells with dense nuclei that are in close contact with the luminal secretory cells. Glycogen production gives cells a clear cytoplasm when stained with H&E. Contain myofibrils that allow the cells to contract to help in milk secretion.
Lactose and proteins
Distended ductal tree
Moderately atrophic lobules
Increased density of intralobular CT