RT Book, Section A1 Ellison, E. Christopher A1 Zollinger, Robert M. SR Print(0) ID 1127274661 T1 BREAST ANATOMY AND INCISIONS T2 Zollinger's Atlas of Surgical Operations, 10e YR 2016 FD 2016 PB McGraw-Hill Education PP New York, NY SN 978-0-07-179755-9 LK accesssurgery.mhmedical.com/content.aspx?aid=1127274661 RD 2024/03/28 AB The regional anatomy of the breast is illustrated in figures 1 and 2. The principal blood supply to the breast comes from the medial perforating branches of the internal mammary artery and vein after they transverse the pectoralis major muscle and its anterior investing fascia. The medial aspect of the breast has lymphatic drainage into the internal mammary chain of lymph nodes within the chest; however, this is quite variable. The majority of the lymphatics from the breast drain to the axillary lymph node basin. The most proximal node or nodes may be located in atypical locations such as within the breast in the axillary tail of the upper/outer quadrant or very low on the lateral chest wall. The identification of these nodes using radionuclide tags and blue dye localization techniques is one of the additional benefits of a sentinel lymph node dissection. Axillary lymph nodes have been grouped into three levels defined by their anatomic relationship to the pectoralis minor muscle (figure 2). Level I nodes are defined as those lateral to the edge of the pectoralis minor muscle. This area includes the external mammary, subscapular, and lateral axillary nodes. Level II nodes are behind or posterior to the muscle and are commonly defined as the central axillary lymph nodes. Level III nodes are located medial or superior to the pectoralis minor muscle. This group includes the subclavicular or apical lymph nodes. They reside in the apex of the axillary space behind the clavicle and deep to the axillary vein. In general, level I and II nodes are removed in axillary lymph node dissections (ALNDs). The overall boundaries of this standard ALND are the chest wall (serratus anterior muscle) medially, axillary vein superiorly, subscapularis muscle plus thoracodorsal and long thoracic nerves posteriorly, and latissimus dorsi laterally.