Mills Ch3 Breast

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SECTION II : Breast

FIGURE 3.14  Cross section through the nipple. The irregular, pleated, or serrated contour of the nipple ducts is evident.

FIGURE 3.15  High-power view of nipple dermis/stroma, demonstrating prominent bundles of smooth muscle fibers.

may extend to within less than 1 mm of the basal layer of the epidermis (58). While the nipple–areola complex lacks pilosebaceous units and hairs except at the periphery of the areola, the dermis contains numerous sebaceous glands. Some of these glands open directly onto the surface of the nipple and areola, whereas others drain into a lactiferous duct or share a common ostium with a lactiferous duct. The tubercles of Montgomery represent a unit consisting of a sebaceous apparatus and an associated lactiferous duct (Fig. 3.16) (59). During pregnancy, these tubercles become increas- ingly prominent. Apocrine sweat glands may also be seen in the dermis of the nipple and areola. Another finding that may occasionally be encountered within the breast parenchyma is the presence of intrama- mmary lymph nodes (60,61). These lymph nodes may be identified as an incidental finding in breast tissue removed

because of another abnormality, or they may be seen as den- sities on mammograms (62).

PREGNANCY AND LACTATION It is not until pregnancy that full development of the breast occurs in humans. During pregnancy, epithelial cell prolif- eration resumes. There is a dramatic increase in the number of lobules, as well as in the number of acinar units within each lobule secondary to epithelial cell proliferation and lobuloalveolar differentiation under the influence of estro- gen, progesterone, prolactin, and growth hormone; growth is further enhanced by adrenal glucocorticoids and insu- lin. This lobular development and expansion occurs at the expense of both the intralobular and extralobular stroma. By

A

B

FIGURE 3.16  Montgomery areolar tubercle. A: Low-power view. B: Higher-power view. These tubercles are units composed of a lactiferous duct and associated sebaceous gland.