Patho5-2_Breast [Dr. Yanez]

PATHOLOGY Dr. Soccorro Cruz-Yanez

January 3, 2012

NORMAL ANATOMY OF THE BREAST   

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In humans, paired mammary mammary glands rest on the pectoralis pectoralis muscle on the upper chest wall The breasts are composed of specialized epithelium and stroma that may give rise to both benign and malignant lesions. Histologically, the following are present: o  Lobe – Lobe – 10  10 in one whole breast Lobule – Many  Many per lobe o  Lobule – Acinus/Alveolus – Many  Many (5-10) per lobule o  Acinus/Alveolus –  Functional secretory unit of the breast  The pathology of the breast is related to the origin of the functional anatomy of the particular area. Ducts – Intra  Intra or interlobular leading to the lactiferous ducts o  Ducts – in the nipple and is the non-secretory that just conducts milk 6 – 10  – 10 major ductal system, subdivided into lobules Successive branching of the large ducts eventuall eventually y leads to to the terminal duct lobular unit In adult women, the terminal duct branches into a grapelike cluster of small acini to form a lobule Each ductal system typically occupies more than one quadrant of the breast, and the systems extensively overlap one another Drains to lactiferous sinuses

Histology Mammary Lobules - The secretory units of the breast - Each lobule consists of a variable variable number of acini, acini, or glands, embedded within loose connective tissue and connecting to the intralobular duct - Each acinus is lined by by two types of cells, 1. Epithelial 2. Myoepithelial 1. Epithelial or ductal cells (columnar, luminal location) - Luminal epithelial cells cells overlay the myoepithelial cells. - Only the lobular luminal cells are are capable of producing milk. - Responsible for secretion 2. Myoepithelial (investing, Myoepithelial  (investing, basal location) - Also known as Sentinel Cells - When these cells are present, it indicates the presence of a benign Lesion - Contractile myoepithelial cells containing myofilaments myofilam ents lie in a meshlike pattern on the basement membrane. - These cells assist in milk ejection  ejection   during lactation and provide structural support to the lobules

Fig. 3. Normal 3. Normal histology of breast acinus

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Fig. 1. Normal 1. Normal breast histology

Notes:  Functional unit of secretion of milk for nourishment of baby  Made up of several lobules of mammary breast draining into the nipple  Drainage of lymphatic channels  –  Disease of breast, st   particularly  particularly malignancy, malignancy, breast carcinoma: carcinoma: 1   line of ar y n o d e metastasis is regional lymph node, particular a x i l l ar (80-90%), internal mammary group of chain of lymph node,  particularly  particularly the inner quadrant of the breast, breast, and supraclavicular group of lymph node.

Lymphatic Drainage  

Axillary – Axillary  – Most  Most common site because tumor cells in the outer quadrant travels this drainage  Internal Mammary – Mammary  – Where  Where tumor cells in the Inner Quadrant enter and travel to the intrathoracic artery   Supraclavicular  –   –  If this is affected, it indicates a more advanced stage of a disease

Fig. 2. Lymphatic 2. Lymphatic drainage of the breast

SECTION B

There are also 2 types of breast stroma : 1. Interlobular stroma  –   –  Consists of dense fibrous connective tissue admixed with adipose tissue. 2. Intralobular stroma – stroma  – Envelopes  Envelopes the acini of the lobules and consists of breast-specific hormonally responsive fibroblast-like cells admixed with scattered lymphocytes. There is important cross-talk between breast epithelium and stroma that promotes the normal structure and function of the breast.

3 Normal phases of breast development: 1. Active – Active – Gland  Gland and Stroma ratio are equal (50:50) 2. Lactating - Mostly glands - There are more glands than stroma due to an increase in the secretion and proliferation of glands - This can be observed in pregnancy - This enlargement isn‟t purely fatty but because there‟s an increase in the number of lobules. (>>>50/50) - Active production of of milk, after pregnancy pregnancy 3. Atrophic - Mostly stroma - More strome strome than glands (