ABC of breast diseases. Management of regional nodes in breast cancer.

Abstract

Lymph drainage from the breast is important in relation to malignant disease and is via the axillary and internal mammary nodes. To a lesser extent lymph also drains by intercostal routes to nodes adjacent to the vertebra. The axillary nodes receive about three quarters of the total lymph drainage, and this is reflected in the greater frequency of tumour metastases to these nodes. FIG Lymph drainage of breast The axillary nodes, which lie below the axillary vein, can be divided into three groups in relation to the pectoralis minor muscle: level I nodes lie lateral to the muscle; level II (Central) nodes lie behind the muscle; and level III (apical) nodes lie between the muscle's medial border, the first rib, and the axillary vein. There are on average 20 nodes in the axilla, with about 13 nodes at level I, five at level II, and two at level III. The drainage from level I nodes passes into the central nodes and on into the apical nodes. An alternative route, by which lymph can get to level III nodes without passing through nodes at level I, is through lymph nodes on the undersurface of the pectoralis major muscle, the interpectoral nodes. The orderly drainage of lymph explains why very few patients with cancer have lymph nodes involved at levels II or level III without involvement at level I. These so called skip metastases are seen in less than 5% of patients with axillary node involvement. FIG Levels of axillary nodes #### Factors associated with lymph node involvement Preoperative clinical or radiological assessment of lymph node involvement is inaccurate, with only 70% of involved nodes being clinically detectable. Only histopathological assessment of excised nodes …