Mastectomy with Axillary Lymph Node Clearance: Surgical Anatomy and Technique

1. Surgical Anatomy of the Breast

Boundaries

• Pectoralis major (upper medial)
• Serratus anterior (inferolateral)
• External abdominal oblique and upper rectus sheath (inferior)

Fascial Layers

• The breast parenchyma sits within the superficial fascia of the anterior thoracic wall
• Posteriorly, the deep investing fascia of pectoralis major (pectoralis fascia) forms the deep boundary - this is excised en bloc with the breast during mastectomy
• The clavipectoral fascia (deep to pectoralis minor) must be incised to enter the axilla during nodal clearance

Cooper's Ligaments

Breast Parenchyma

2. Blood Supply

3. Innervation

• Sensory: Lateral and anterior cutaneous branches of intercostal nerves T2-T6 supply the breast parenchyma and skin. The upper breast is also supplied by anterior branches of the supraclavicular nerve (cervical plexus, C3-C4).
• The intercostobrachial nerve (lateral cutaneous branch of T2) crosses the axilla medially to laterally to reach the medial upper arm. It is often sacrificed during axillary dissection, causing sensory loss/numbness over the medial arm; preservation should be attempted when possible.

4. Lymphatic Drainage of the Breast

1. Intrinsic (primary) - interlobular and along lactiferous ducts within the gland
2. Subareolar plexus - drains skin, nipple/areola, and central gland
3. Deep (posterior) plexus - on the deep surface, communicates with fascia of pectoralis

5. Axillary Anatomy

• Anterior wall: Pectoralis major, pectoralis minor, clavipectoral fascia
• Posterior wall: Subscapularis, teres major, latissimus dorsi
• Medial wall: Serratus anterior + upper 4-5 ribs
• Lateral wall: Humerus / bicipital groove
• Apex: Cervicoaxillary canal (bounded by clavicle anteriorly, scapula posteriorly, 1st rib medially) - communicates with posterior triangle of neck
• Base: Axillary fascia and skin

Axillary Lymph Node Levels (defined relative to pectoralis minor)

6. Key Structures at Risk During ALND - Critical Surgical Anatomy

Thoracodorsal Neurovascular Bundle

• Nerve: branch of posterior cord of brachial plexus (C6, C7, C8); artery: branch of subscapular artery
• Enters the axilla in a deep posterior position, approximately halfway between the chest wall and latissimus muscle - typically in the center of the specimen
• Identified and must be preserved - injury causes weakness of shoulder adduction/internal rotation (latissimus dorsi paralysis), limiting arm movements and affecting reconstructive options (TRAM/LD flap)
• The thoracodorsal vein is a major tributary of the axillary vein; care needed to distinguish it from the anterior thoracoepigastric vein (which must be ligated)

Long Thoracic Nerve (Nerve of Bell)

• Arises from roots C5, C6, C7
• Runs vertically along the medial chest wall (serratus anterior surface), entering the muscle inferiorly
• Carefully protected against the chest wall throughout the dissection; can be pulled laterally by retractors and must be specifically sought if not visible
• Injury causes winged scapula (serratus anterior paralysis)

Intercostobrachial Nerve

• Lateral cutaneous branch of T2 intercostal nerve
• Runs horizontally (medial to lateral) across the axillary field - easily distinguished from the vertically running thoracodorsal and long thoracic nerves
• Sacrifice causes numbness/dysesthesia over the medial upper arm; preservation is attempted but often not possible

Axillary Vein

• Forms the superior boundary of the ALND
• Identified laterally first (safest approach - no critical structures laterally) by following the anterior surface of latissimus dorsi superiorly where the vein crosses its tendinous portion
• Dissection must not go superior to the axillary vein - this dramatically worsens lymphedema risk
• Small venous tributaries on the inferior aspect are clipped and divided as dissection proceeds medially

Brachial Plexus

• Located superior to the axillary vein; not typically encountered in standard levels I-II dissection
• At risk with level III dissection or aggressive superior dissection

7. Types of Mastectomy

8. Operative Steps: Modified Radical Mastectomy

Patient Setup

• Supine; ipsilateral arm extended and widely prepped
• General anaesthesia (regional block e.g. thoracic paravertebral block is a useful adjunct)
• Prophylactic antibiotics, sequential compression devices

Mastectomy Phase

1. Incision: Broad transverse-oblique ellipse encompassing the nipple-areolar complex; orientation facilitates subsequent axillary dissection
2. Flap elevation: Raise mastectomy flaps in the avascular plane between breast parenchyma and subcutaneous fat, extending to:
   • Clavicle superiorly
   • Lateral sternal edge medially
   • Rectus sheath/inframammary fold inferiorly
   • Anterior border of latissimus dorsi laterally
   • Include the axillary tail of Spence during the superolateral dissection
3. Chest wall dissection: Breast and pectoralis fascia are excised off the pectoralis major muscle (from superior to inferior). Small perforating vessels from pectoralis are controlled with electrocautery/clips.
4. Medial hemostasis: Internal mammary perforators are identified in the intercostal spaces and ligated at the sternal border
5. The breast may be left in continuity with axillary tissue for en bloc ALND

Axillary Lymph Node Dissection Phase

1. Enter the axilla: Incise the clavipectoral fascia at the lateral border of pectoralis major, progressing superiorly toward the apex
2. Identify the axillary vein: Follow latissimus dorsi anteriorly/superiorly until the vein crosses its tendinous band (lateral approach - safest)
3. Vein dissection: Dissect fatty and nodal tissue off the inferior aspect of the axillary vein from lateral to medial, clipping all small tributaries. Do not go superior to the vein.
4. Identify thoracodorsal bundle: Located centrally/posteriorly in the axilla. Identify and protect throughout.
5. Identify long thoracic nerve: Along medial chest wall, running vertically over serratus anterior. Preserve against the chest wall; ease retractors if not seen.
6. Intercostobrachial nerve: Running horizontally - attempt preservation but may sacrifice for exposure
7. Rotter's space: Palpate and inspect for involved Rotter's nodes between the two pectoralis muscles; the medial pectoral neurovascular bundle is identified here and may be preserved or ligated depending on nodal involvement
8. Apex dissection: Connect cleared axillary vein to the chest wall below pectoralis minor. Mobilize the nodal specimen inferiorly, divide tissue between thoracodorsal and long thoracic nerves (included in specimen)
9. Final sweep: Blunt sweep clears specimen from the latissimus/subscapularis floor. Anterior branches of thoracodorsal bundle are clipped and divided.
10. Verification: Visually confirm or stimulate thoracodorsal and long thoracic nerves for integrity; palpate for residual adenopathy in Rotter's space and level III

9. Closure and Drainage

• Two closed-suction (Jackson-Pratt) drains: one looped into the apex of the axilla, one under the mastectomy flap
• Wound closed in layers (deep dermal interrupted + subcuticular skin closure)
• Compression binder/wrap applied
• Drains removed when output falls below 30 mL per 24-hour period (sequentially, not same day)

10. Complications and Their Anatomical Basis

• Mulholland and Greenfield's Surgery: Scientific Principles and Practice, 7e - Surgical Anatomy of the Breast, pp. 3866-3870
• Current Surgical Therapy, 14e - Mastectomy and Axillary Lymph Node Dissection, pp. 778-809