Anatomy

The mature adult breast is composed of fatty tissue and parenchyma in which terminal ductulo-lobular units of epithelium are surrounded by fibrous connective tissue stroma. There are about 15-25 lobes of parenchymatous elements associated with each of the lactiferous ducts which drain into the nipple. The presence of this functional lobar arrangement provides an anatomical framework for some surgical procedures such as major duct excision and quadrantectomy for cancer. The anatomical boundaries of the breast are not well defined except at the deep surface where the gland overlies the pectoralis fascia. The general topographical anatomy of the breast is illustrated in Figure 11.1

Figure 11.1. Topographical anatomy of the right breast. Reproduced with permission from Hermanek P, Hutter RVP, Sobin LH, Wagner G, Wittekind Ch (eds.). TNM Atlas: illustrated guide to the TNM/pTNM classification of malignant tumours, 4th edition. Springer-Verlag: Berlin and Heidelberg, 1997.

Pectoralis minor muscle

Figure 11.2. Breast: regional lymph nodes. Reproduced from Hermanek P, Hutter RVP, Sobin LH, Wagner G, Wittekind Ch (eds.). TNM Atlas: illustrated guide to the TNM/pTNM classification of malignant tumours, 4th edition. Springer-Verlag: Berlin and Heidelberg, 1997.

Pectoralis minor muscle

Figure 11.2. Breast: regional lymph nodes. Reproduced from Hermanek P, Hutter RVP, Sobin LH, Wagner G, Wittekind Ch (eds.). TNM Atlas: illustrated guide to the TNM/pTNM classification of malignant tumours, 4th edition. Springer-Verlag: Berlin and Heidelberg, 1997.

1. Axillary (ipsilateral): interpectoral (Rotter) nodes and lymph nodes along the axillary vein and its tributaries which may be divided into the following levels:

i) Level I (low axilla): lymph nodes lateral to the lateral border of pectoralis minor muscle ii) LevelII(mid-axilla): lymph nodes between the medial and lateral borders of the pectoralis minor muscle and the interpectoral (Rotter) lymph nodes iii) Level III (apical axilla): lymph nodes medial to the medial margin of the pectoralis minor muscle including those designated as subclavicular or apical

Note: Intramammary lymph nodes are coded as axillary lymph nodes

2. Internal mammary (ipsilateral): lymph nodes in the intercostal spaces along the edge of the sternum in the endothoracic

Any other lymph node metastasis is coded as a distant metastasis (M1), including supreclavicular, cervical or contralateral internal mammary lymph nodes

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