Breast Development

• Overview
• Congenital and Developmental Abnormalities of the Breast


Milk Line*
During the fifth week of human develoment, the embryo develops a milk line that extends from the armpit to the groin. This usually disappears forming the breast tissue. In 2-6% of women however this band persists and accessory breast tissue can occur anywhere along this line. This accessory tissue may be in the form of accessory nipples to fully developed and functioning breast tissue.

The importance of accessory breast tissue is that it is susceptible to disease processes of the breast. At the time of delivery, colostral milk (witches milk) can be expressed from the nipple for 4-7 days postpartum in either sex. This secretion usually declines over the next 3 to 4 week period.

Approximately one year prior to the onset of menses, females develop a breast bud or an area of firmness under the nipple areolar complex, which may be associated with some sensitivity and tenderness. This development is in response to the release of pituitary (FSH and LH) and subsequent ovarian hormones (estrogen and progesterone).

Mistaking this process of normal growth and development for a pathologic condition and subsequent biopsy or destruction of the breast bud with trauma can result in severe deformity of the breast. The breast continues its maturation process throughout the adolescent years but is never fully developed until lactation (milk production).


Breast Development

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Congenital and Developmental Abnormalities of the Breast

The most common abnormality of development is the development of an accessory nipple that can occur along the milk line and is frequently mistaken for a mole. Accessory breast tissue can occur anywhere along this line and occasionally function if associated with a nipple during lactation (milk production).

Underdevelopment of the breast (hypoplasia) or congenital absence of the breast (amazia) can occur. Most of these abnormalities are not severe. The severest deformity, amastia (absent breast) or hypoplasia (underdeveloped breast) occur with underlying abnormalities of the pectoralis muscle, 90% of the time (Polands syndrome; congenital absence or underdeveloped breast, pectoralis muscle and rib cage).

Virginal hypertrophy is the asymmetric and excessive growth of one breast, over the other, during adolescence. This can be corrected with surgery during the twenties, allowing the opposite breast an opportunity to catch up.


Virginal Hypertrophy**

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Quick Facts:

• The breast is never fully developed until lactation (milk production).
• 90% of the time breast tenderness is benign (not cancer).
• Breast cancer is usually painless.

* ** Copyright 1965. Icon Learning Systems, LLC, a subsidiary of MediMedia USA Inc. Reprinted with permission from ICON Learning Systems, LLC, illustrated by Frank H. Netter, MD. All rights reserved.