breast

The breast receives its principal blood supply from (1) perforating branches of the internal mammary artery; (2) lateral branches of the posterior intercostal arteries; and (3) branches from the axillary artery, including the highest thoracic, lateral thoracic, and pectoral branches of the thoracoacromial artery (Fig. 16-6). The second, third, and fourth anterior intercostal perforators and branches of the internal mammary artery arborize in the breast as the medial mammary arteries. The lateral thoracic artery gives off branches to the serratus anterior, pectoralis major and minor, and subscapularis muscles. It also gives rise to lateral mammary branches. The veins of the breast and chest wall follow the course of the arteries with venous drainage being toward the axilla. The three principal groups of veins are (1) perforating branches of the internal thoracic vein; (2) perforating branches of the posterior intercostal veins; and (3) tributaries of the axillary vein.

The 6 axillary lymph node groups recognized by surgeons (Figs. 16-7 and 16-8) are (1) the axillary vein group (lateral) that consists of 4 to 6 lymph nodes, which lie medial or posterior to the vein and receive most of the lymph drainage from the upper extremity; (2) the external mammary group (anterior or pectoral group) that consists of 5 or 6 lymph nodes, which lie along the lower border of the pectoralis minor muscle contiguous with the lateral thoracic vessels and receive most of the lymph drainage from the lateral aspect of the breast; (3) the scapular group (posterior or subscapular) that consists of 5 to 7 lymph nodes, which lie along the posterior wall of the axilla at the lateral border of the scapula contiguous with the subscapular vessels and receive lymph drainage principally from the lower posterior neck, the posterior trunk, and the posterior shoulder; (4) the central group that consists of 3 or 4 sets of lymph nodes, which are embedded in the fat of the axilla lying immediately posterior to the pectoralis minor muscle and receive lymph drainage both from the axillary vein, external mammary, and scapular groups of lymph nodes and directly from the breast; (5) the subclavicular group (apical) that consists of 6 to 12 sets of lymph nodes, which lie posterior and superior to the upper border of the pectoralis minor muscle and receive lymph drainage from all of the other groups of axillary lymph nodes; and (6) the interpectoral group (Rotter's) that consists of 1 to 4 lymph nodes, which are interposed between the pectoralis major and pectoralis minor muscles and receive lymph drainage directly from the breast. The lymph fluid that passes through the interpectoral group of lymph nodes passes directly into the central and subclavicular groups.

Common sites of involvement, in order of frequency, are bone, lung, pleura, soft tissues, and liver.