Breast development is under the control of prolactin, GH, estrogen, progesterone, and adrenocorticoids.
Estrogen & Progesterone (Steroids)
Estrogen & Progesterone receptors are located in the nucleus
Assessment is done on ER/PR status to evaluate biologic characteristics of a breast cancer
If tumor is positive for ER/PR +, then can give anti-hormonal therapy (Letrozole or tamoxifen)
High estrogen & progesterone levels (after ovulation) = breast fullness (body is preparing for making a baby)
Increased lobular acini
Epithelial cells become vacuolated
Interlobular stromal edema increases
Decreased levels of estrogen & progesterone (menstruation)
Apoptosis of epithelial cells
Reduction in stromal edema
Oxytocin
Responsible for “milk letdown”
Nipple stimulation causes posterior pituitary to release stored oxytocin which then causes myoepithelial cells to contract/eject milk from the nipple.
Prolactin
Responsible for breast secretory activity (lactogenic)
Made in anterior pituitary
Initial secretory products= colostrum
Low lipid content
High protein (including maternal immunoglobulins which help protect baby from infections during initial 6 months of life)
Breast Changes during pregnancy
In pregnancy, elevated prolactin, estrogen, and progesterone increase development of the tubuloalveolar glands but inhibit milk production.
Lactational Changes in the breast
Lactation occurs when estrogen and progesterone levels fall dramatically at birth while prolactin levels remain high and oxytocin levels increase to stimulate milk release. In the absence of pregnancy or suckling (active nursing), the tubuloalveolar glands regress and become inactive.
Notice the expanded and increased number of acini in the lactating breast below. Some acinar epithelial cells become vacuolated with increased secretions in anticipation of lactation.
Some patients may present with a mass during pregnancy or lactation. Histologic evaluation reveals abundant lactatational changes consistent with a lactational adenoma.
The following image (onlinemidwife 2012) demonstrates the complexities of hormonal response in the breast.
Menopausal Changes in the Breast
After menopause, the glandular tissue largely atrophies and is replaced by fat, although some of the lactiferous ducts may remain. Notice the increased fibrous tissue
