Breast disease in women encompasses a spectrum of benign and malignant disorders, which present most commonly as breast pain, nipple discharge, or palpable mass. The specific causes of these symptoms vary with patient age. Benign disorders predominate in young premenopausal women, whereas malignancy rates increase with advancing age. Evaluation of breast disorders usually requires the combination of a careful history, physical examination, imaging, and when indicated, biopsy.
The glandular portion of the breast is comprised of 12 to 15 independent ductal systems that each drain approximately 40 lobules (Fig. 12-1). Each lobule consists of 10 to 100 milk-producing acini that drain into small terminal ducts (Parks, 1959). Terminal ducts drain into larger collecting ducts that merge into even larger ducts, which exhibit a saccular dilation just below the nipple called a lactiferous sinus (Fig. 12-2).
A. Ductal anatomy of the breast. (From Going, 2004, with permission.) B. Terminal duct-acinar structure from a fine-needle aspiration biopsy. C. Histology of a normal lobule.
In general, only six to eight openings are visible on the nipple surface. These drain the dominant ductal systems, which account for approximately 80 percent of the breast's glandular volume (Going, 2004). Minor ducts either terminate just below the nipple surface or open on the areola near the base of the nipple. The areola itself contains numerous lubricating sebaceous glands, called Montgomery glands, which are often visible as punctate prominences.
In addition to epithelial structures, the breast is composed of varying proportions of collagenous stroma and fat. The distribution and abundance of these stromal components accounts for a breast's consistency when palpated and for its imaging characteristics.
Afferent lymphatic drainage of the breast is provided by dermal, subdermal, interlobar, and prepectoral systems (Fig. 12-3) (Grant, 1953). Each of these may be viewed as a lattice of valveless channels that interconnect with every other system and that ultimately drain into one or two axillary lymph nodes (the sentinel nodes). Because all of these systems are interconnected, the breast drains as a unit, and injection of colloidal dyes in any part of the breast at any level will result in accumulation of dye in the same one or two axillary sentinel lymph nodes. The axillary lymph nodes receive most of the lymphatic drainage of the breast, and consequently are the nodes most frequently involved with breast cancer metastases (Hultborn, 1955). However, there are also alternate drainage pathways that do not appear to interconnect with other networks and that drain directly into internal mammary, supraclavicular, contralateral axillary, ...