ABSTRACT
The breast is a skin appendage which develops from modified sweat glands deep to the nipple. Accessory breast tissue may occur along a line from groin to axilla. The development of the rudimentary breast is stimulated by hormones, and commences as a nodule or breast bud deep to the areola in early puberty. The adult breast lies predominantly on the deep fascia of pectoralis major and extends from the second to the sixth costal cartilages. Medially, it extends almost to the midline and laterally it continues as the axillary tail of the breast over the lateral edge of pectoralis major into the axilla. Superficially, it is separated from the skin by subcutaneous fat, except over the areola and the nipple. The breast substance consists of glandular tissue and surrounding fat. Alterations in hormonal levels cause structural and functional changes in the breast during pregnancy, lactation and, to a lesser extent, throughout the menstrual cycle.
