Position the patient with the arm extended on an armboard with a bump under the shoulder if necessary (see Chapter 17). If sentinel node biopsy has been performed at an earlier time, plan an incision which excises and extends the previous scar. If sentinel node biopsy was done during the same operative procedure and returned positive, then extend the sentinel node incision in both directions.

In general, an oblique incision just lateral to the lateral border of the pectoralis major muscle provides excellent access to the axilla. Placing the incision just lateral to the muscle edge allows the scar to fall behind the muscle, where it is less noticeable. A more cosmetically appealing transverse or U-shaped incision may be used. This transverse incision should be planned to lie below the hair-bearing portion of the axilla. Patient habitus and location of sentinel lymph node may lead one incision or the other to be preferable in a specific situation. Create skin flaps to expose the subcutaneous tissues.

Discrete superficial and deep fascia is not encountered in the axilla. Instead, the axillary fascia (derived from the fascia of the pectoralis major, latissimus dorsi, and serratus anterior muscles as well as the fascia investing the muscles of the arm) is adherent to the superficial fascia and is, in the hollow of the armpit, along with the suspensory ligament of the axilla, a continuation of the clavipectoral fascia.

The axillary lymph nodes are predominantly located on the medial side of the axillary neurovascular bundle, and along the medial axillary wall. For convenience, these are described in five groups by anatomists. Terms in parentheses indicate the approximate equivalent in Haagensen’s system. The lateral group (axillary), on the third part of the axillary neurovascular bundle, drains the upper limb. The subscapular (scapular) or posterior group, located around the subscapular artery and vein, drains the shoulder and posterior thorax. The pectoral (external mammary) group, which is associated with the lateral thoracic
vessels along the inferolateral border of the pectoralis major muscle, drains and receives lymph from the anterior thoracic wall, including the lateral breast. These three groups drain into the central group of (central) lymph nodes, which is located approximately on the second part of the axillary neurovascular bundle. The apical group (subclavian), associated with the first part of the axillary neurovascular bundle, receives lymphatics from the central group as well as from the upper outer quadrant of the mammary gland.

Surgeons commonly use a different terminology (topographic) for axillary lymph nodes. Topographic group I nodes include the pectoral, subscapular, and lateral nodes. These are the nodes lateral to the pectoralis minor muscle. Topographic group II nodes are under the pectoralis minor muscle and correspond to the central nodes, whereas topographic group III nodes are medial to the pectoralis minor muscle and correspond to the apical nodes (see orientation figure).