Mills Ch3 Breast

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CHAPTER 3:  Breast

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FIGURE 3.2  Adolescent breast tissue composed of branching ducts with rudimentary lobule development (type 1 lobules). The stroma consists of a mixture of fibrous connective tissue and adipose tissue. A: Scanning magnification. B: High power.

The adolescent male breast is composed of fibroadipose tissue and ducts lined by low cuboidal cells.

the nonlactating adult breast, and the relative proportions of fibrous tissue and adipose tissue vary with age and among individuals (Fig. 3.3). The ductal-lobular system of the breast is arranged in the form of segments, or lobes. While these segments can be readily appreciated by injecting the ductal system with dyes or radiologic contrast agents (Fig. 3.4), they are ana- tomically poorly defined, and no obvious boundaries can be appreciated between these segments during surgery, upon gross inspection of mastectomy specimens, or on histologic examination. In addition, these segments show consider- able individual variation with regard to their extent and dis- tribution (11), and the ramifications of individual segments may overlap. The segmental nature of some neoplastic pro- cesses in the breast, particularly ductal carcinoma in situ, is now widely appreciated. This recognition, in conjunction with observations in developmental anatomy and morphol- ogy, has led to the development of the “sick lobe” hypoth- esis of breast cancer (12,13). This theory postulates that early breast carcinoma (ductal carcinoma in situ) is a lobar disease, often isolated to a single ductal system (or lobe). Thus, surgical resection of the involved lobe or segment is an important therapeutic goal. Unfortunately, since it is not possible for the surgeon to define intraoperatively the boundaries of the involved segment, performing a “segmen- tectomy” to remove the entirety of a diseased segment is at this time more of a theoretical concept than a practically attainable goal. Each segment consists of a branching structure that has been likened to a flowering tree (Fig. 3.5) (14). The lob- ules represent the flowers, draining into ductules and ducts (twigs and branches), which, in turn, drain into the collect- ing ducts (trunk) that open onto the surface of the nipple. Just below the nipple, the ducts expand to form lactiferous sinuses. The sinuses terminate in cone-shaped ampullae just below the surface of the nipple.

THE ADULT FEMALE BREAST The size of the breast is greatly influenced by the indi- vidual’s body habitus since the breast is a major reposi- tory for fat; it can range in size from 30 g to more than 1,000 g. The breast lies on the anterior chest wall over the pectoralis major muscle and typically extends from the 2nd to the 6th rib in the vertical axis and from the sternal edge to the mid-axillary line in the horizontal axis. Breast tissue also projects into the axilla as the tail of Spence. The breast extends laterally over the serratus anterior muscle and inferiorly over the external oblique muscle and the superior rectus sheath. The breast lies within a space in the superficial fascia, which is continu- ous with the cervical fascia superiorly and the superficial abdominal fascia of Cooper inferiorly. The only bound- ary of the breast that is anatomically well defined is the deep surface where it abuts the pectoralis fascia. How- ever, despite this macroscopic demarcation, microscopic foci of glandular tissue may extend into and even through the pectoral fascia and may traverse the other anatomic boundaries described above. The clinical significance of this observation is that even total mastectomy does not result in removal of all glandular breast tissue. Bundles of dense fibrous connective tissue, the suspensory liga- ments of Cooper, extend from the skin to the pectoral fascia and provide support to the breast. The adult female breast consists of a series of ducts, ductules, and lobular acinar units embedded within a stroma that is composed of varying amounts of fibrous and adipose tissue. The stroma comprises the major portion of