1. introduction to breast pathology.pdf

introduction to breast pathology Lesions of the female breast are much more common than lesions of the male breast. These lesions usually take the form of: 1. palpable, 2. sometimes painful, 3. nodules or masses. Fortunately, most are innocent, Common clinical symptoms of breast disease THE FEMALE B...

introduction to breast pathology Lesions of the female breast are much more common than lesions of the male breast. These lesions usually take the form of: 1. palpable, 2. sometimes painful, 3. nodules or masses. Fortunately, most are innocent, Common clinical symptoms of breast disease THE FEMALE BREAST mammary glands or breasts are highly modified apocrine sweat glands develop embryologically along two lines, the milk lines, extending from the axillae to the groins. In humans, only one gland develops on each side of the thorax, although accessory breast tissue may be found anywhere along the milk lines. In humans, paired mammary glands rest on the pectoralis muscle on the upper chest wall. The breasts of both sexes follow a similar course of development until puberty, after which the female breasts develop under the influence of pituitary, ovarian and other hormones. Until the menopause, the breasts undergo cyclical changes in activity, which are controlled by the hormones of the ovarian cycle. After menopause, the breasts, like the other female reproductive tissues, undergo progressive atrophy and involution. The breasts are composed of : 1.specialized epithelium 2.stroma that may give rise to both benign and malignant lesions Anatomic origins of common breast lesions. normal histology of the breast varies according to: 1. 2. 3. 4. 5. gender, age, menopausal status, phase of the menstrual cycle, pregnancy, and lactation, among other factors. FIGURE 23-2 Life cycle changes. B, The density of a young woman's breast stems from the predominance of fibrous interlobular stroma and the paucity of adipose tissue. Before pregnancy the lobules are small and are invested by loose cellular intralobular stroma. Larger ducts connect lobules. C, During pregnancy, branching of terminal ducts produces more numerous, larger lobules. Luminal cells within lobules undergo lactational change, a precursor to milk formation. D, With increasing age the lobules decrease in size and number, and the interlobular stroma is replaced by adipose tissue. A, Mammograms in young women are typically radiodense or white in appearance, making massforming lesions or calcifications (which are also radio dense) difficult to detect E, Mammograms become more radiolucent with age as a result of the increase in adipose tissue, which facilitates the detection of radio dense mass-forming lesions and calcifications EPITHELIUM OF THE BREAST Two cell types line the ducts and lobules: 1. Contractile myoepithelial cells : containing myofilaments. lie on the basement membrane. assist in milk ejection during lactation and provide structural support to the lobules. 2. Luminal epithelial cells : overlay the myoepithelial cells. Only the lobular luminal cells are capable of producing milk. STROMA OF THE BREAST There are two types of breast stroma. 1- The interlobular stroma: consists of dense fibrous connective tissue admixed with adipose tissue. 2- The intralobular stroma : envelopes the acini of the lobules and consists of fibroblast-like cells admixed with scattered lymphocytes., plasma cells, macrophages, and mast cells changes in the breast during menstrual cycle Just as the endometrium grows and ebbs with each menstrual cycle, so does the breast. In the first half of the menstrual cycle the lobules are relatively quiescent. After ovulation, under the influence of estrogen and rising progesterone levels, cell proliferation increases, as does the number of acini per lobule. The intralobular stroma also becomes markedly edematous. Upon menstruation, the fall in estrogen and progesterone levels induces the regression of the lobules and the disappearance of the stromal edema. changes in the breast during pregnancy & lactation Under the influence of oestrogens and progesterone produced by the corpus luteum and later by the placenta, the terminal duct epithelium proliferates to form greatly increased numbers of : 1. lobules 2. secretory acini. Breast proliferation is also dependent on: 1. prolactin, 2. human chorionic somatomammotropin (a prolactin-like hormone produced by the placenta), 3. thyroid hormone 4. corticosteroids. 5. growth hormone 6. insulin. Only with the onset of pregnancy does the breast become completely mature and functional. Lobules increase progressively in number and size. by the end of the pregnancy the breast is composed almost entirely of lobules separated by relatively scant stroma Immediately after delivery of the baby the luminal cells of the lobules produce colostrum (high in protein), which changes to milk (higher in fat and calories) over the next 10 days as progesterone levels drop. the lactating breast is characterized by distension of the lobular acini as a result of accumulated abundant secretory material and Colostrum is the form of breast secretion available during the first few days after birth; it contains a laxative substance and maternal antibodies. Unlike milk, colostrum contains little lipid. Breast secretion is controlled by the hormone prolactin. During pregnancy, prolactin secretion progressively increases but high levels of circulating oestrogens and progesterone suppress its activity. Properties of breast milk 1. provides complete nourishment from birth until several years of age, 2. provides protection against infection, allergies, and some autoimmune diseases. 3. Maternal antibodies (chiefly secretory IgA), 4. vitamins, 5. enzymes, 6. numerous other mediators (e.g., cytokines, antioxidants, fibronectin, and lysozyme) augment the infant's own developing immune defenses. A neurohormonal reflex in which nipple stimulation by suckling causes release of prolactin from the anterior pituitary controls the process. A different neurohormonal reflex, also initiated by suckling, causes the release of the hormone oxytocin from the posterior pituitary. Oxytocin causes contraction of the myoepithelial cells which embrace the secretory acini and ducts, thus propelling milk into the lactiferous sinuses (milk 'let-down'). Withdrawal of the suckling stimulus, and hence the release of pituitary hormones at weaning, results in regression of the lactating breast and resumption of the ovarian cycle. Upon the cessation of lactation, the breast epithelium and stroma undergo extensive remodeling Epithelial cells undergo apoptosis, lobules regress and atrophy, and the total breast size is diminished. However, full regression does not occur, and as a result pregnancy causes a permanent increase in the size and number of lobules. After the third decade, long before menopause, lobules and their specialized stroma start to involute. Lobular atrophy may be almost complete in elderly females The interlobular stroma also changes, since the radiodense fibrous stroma of the young female is progressively replaced by radiolucent adipose tissue Menopause During the postmenopausal period, with the reduction of estrogen and progesterone levels, there is involution and atrophy of the mammary TDLUs, with reduction in the size and complexity of the acini, and there is loss of the specialized intralobular stroma Ducts may become variably ectatic. The postmenopausal breast is characterized by : 1. a marked reduction in glandular tissue and collagenous stroma, 2. a concomitant increase in stromal adipose tissue. 3. The end stage of menopausal involution is typified by remnants of the TDLUs, typically composed of ducts with atrophic acini, surrounded by hyalinized connective tissue or embedded within adipose tissue with little or no surrounding stroma CONGENITAL ANOMALIES OF THE BREAST 1- Milk line Remnants. (Supernumerary nipples or breasts) result from the persistence of epidermal thickenings along the milk line, which extends from the axilla to the perineum. this phenomenon is most commonly encountered in the axilla, inframammary fold, and vulva The disorders that affect the normally situated breast rarely arise in these heterotopic, hormone-responsive foci, which most commonly come to attention as a result of painful premenstrual enlargements. these congenital anomalies are subject to the same diseases that affect the definitive breasts 2- Accessory Axillary Breast Tissue. In some women the normal ductal system extends into the subcutaneous tissue of the chest wall or the axillary fossa (the “axillary tail of Spence”). This epithelium can undergo lactational changes (resulting in a palpable mass) or give rise to carcinomas outside the breast proper. Accessory nipple, Left Pectoral region INFLAMMATIONS uncommon cause pain and tenderness in the involved areas. Included: several forms of mastitis and traumatic fat necrosis, none of which are associated with increased risk of cancer. Acute mastitis develops when : 1. bacteria gain access to the breast tissue through the ducts; 2. when there is inspissation of secretions; 3. through fissures in the nipples, which usually develop during the early weeks of nursing; 4. or from various forms of dermatitis involving the nipple COMMON ORGANISMS Staphylococcal infections : induce single or multiple abscesses Streptococcal infections : generally spread throughout the entire breast, causing pain, marked swelling, and breast tenderness. Traumatic fat necrosis is an uncommon is significant only because it produces a mass. Most, but not all, women with this condition report some antecedent trauma to the breast.