The primary route of lymphatic drainage of the breast is through the axillary lymph nodes. Axillary lymph nodes can be divided into levels based on location relative to the pectoralis minor muscle. Level 1 lymph nodes include external mammary, axillary vein and scapular lymph node groups and lie lateral to the lateral border of the pectoralis minor muscle. Level 2 nodes include central and some subclavicular lymph node groups and lie behind the pectoralis minor muscle.
Level 3 nodes include the subclavicular nodal group and are located medial to the medial border of the pectoralis minor. These distinctions aid in pathologic examination of surgical specimens. Nodal grouping can also be done based on anatomic location. Table 1.5 is a description of the major nodal groups. Figure 1.5 shows the lymph nodes and veins of the axilla.
Internal Mammary Lymph Nodes
The internal mammary nodes lie in the intercostal spaces in the parasternal region. The nodes lie close to internal mammary vessels in extrapleural fat and are distributed in the intercostal spaces. The number described along the internal mammary chain varies.
Fig. 1.5. Axillary vein and lymph nodes. The axillary vein, its branches and the lymph nodes are shown in situ. The pectoralis major and minor have been reflected back. Reprinted with permission from: Rosse C, Gaddum-Rosse P. Hollinshead’s Textbook of Anatomy. 5th ed. 1997; 217. ©1997 Lippincott-Raven
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Mary L. Gemignani
Memorial Sloan-Kettering Cancer Center