What should I know about breast mastectomy and lymph node dissection as a third-year medical student?

Breast Mastectomy and Lymph Node Dissection: Key Concepts for Third-Year Medical Students

For breast mastectomy and lymph node dissection, you should understand the indications, techniques, complications, and evidence-based practices that guide current management of breast cancer patients.

Types of Mastectomy and Indications

Mastectomy Types

• Modified radical mastectomy: Removal of entire breast and axillary lymph nodes while preserving pectoralis muscles
• Total/Simple mastectomy: Removal of breast tissue only without axillary dissection
• Skin-sparing mastectomy: Preserves skin envelope for reconstruction
• Nipple-sparing mastectomy: Preserves nipple-areolar complex

Indications for Mastectomy

• Multicentric disease
• Large tumor-to-breast ratio
• Extensive microcalcifications 1
• Contraindications to radiation therapy
• Patient preference
• Failed breast-conserving therapy

Lymph Node Management

Sentinel Lymph Node Biopsy (SLNB)

• Technique: Uses blue dye and/or radioactive tracer to identify first draining node(s)
• Standard of care for clinically node-negative early breast cancer 1
• Training requirement: Surgeons should perform 20-30 procedures with concurrent ALND to validate a ≥90% identification rate and ≤10% false-negative rate 1
• Indications: Small primary tumors with clinically negative axilla
• Contraindications: Clinically positive nodes, pregnancy, multicentric disease

Axillary Lymph Node Dissection (ALND)

• Technique: Removal of Level I and II axillary nodes (at least 10 nodes for adequate staging) 1
• Indications:
  • Clinically positive nodes confirmed by FNA or core biopsy
  • Sentinel nodes not identified
  • Positive sentinel nodes in specific circumstances

Current Practice Guidelines

• ACOSOG Z0011 Trial impact: For patients with T1/T2 tumors, ≤2 positive SLNs undergoing lumpectomy and whole breast radiation, ALND can be omitted 1
• For mastectomy patients: ALND is still recommended for positive sentinel nodes 1
• Level I and II dissection: Should include tissue inferior to axillary vein from latissimus dorsi muscle laterally to medial border of pectoralis minor 1
• Level III dissection: Only if gross disease is apparent in level II nodes 1

Complications to Know

Lymphedema

• Incidence: 8-23% after ALND 2
• Risk factors: Age, radiation therapy, infection in operated arm 2
• Definition: ≥10% increase in arm circumference compared to contralateral arm

Other Complications

• ALND vs. SLNB: ALND has significantly higher complication rates (31% vs. 10%) 3
• Common complications:
  • Seroma formation
  • Wound infection
  • Hematoma
  • Nerve injury (intercostobrachial, thoracodorsal, long thoracic)
  • Shoulder dysfunction
  • Lymphedema
  • Pain syndromes 4
• Impact on reconstruction: ALND increases risk of complications in immediate breast reconstruction by 3-fold 3

Post-Mastectomy Radiation Therapy (PMRT)

Indications

• Strong recommendation: 4 or more positive lymph nodes 1
• Consider: 1-3 positive lymph nodes 1
• Fields: Chest wall and regional lymph nodes (supraclavicular, +/- internal mammary)
• Timing: After completion of chemotherapy if indicated

Recent Practice Changes

Deimplementation of Low-Value Procedures

• ALND for limited nodal disease: Decreased by ~50% (from 44% in 2011 to 25-28% in 2013) 1
• Re-excision for close but negative margins: Decreased by ~40% 1
• Contralateral prophylactic mastectomy: Continues to rise despite being low-value in average-risk patients 1
• SLNB in women ≥70 years with hormone-positive cancer: Still performed in >80% of cases despite recommendations against 1

Key Points for Pimping

1. Anatomy: Know the boundaries of axillary levels I, II, and III

   • Level I: Lateral to pectoralis minor
   • Level II: Behind pectoralis minor
   • Level III: Medial to pectoralis minor

2. Berg's levels: Understand the relationship to the pectoralis minor muscle

3. Important nerves:

   • Long thoracic nerve (serratus anterior) - injury causes winging of scapula
   • Thoracodorsal nerve (latissimus dorsi)
   • Intercostobrachial nerve (sensation to upper inner arm)

4. Lymphatic drainage patterns:

   • 75% of breast lymphatics drain to axilla
   • 20% to internal mammary nodes
   • 5% to interpectoral (Rotter's) nodes

5. Sentinel node identification rate: Should be ≥90% with dual technique (blue dye + radiocolloid) 1

6. Z0011 criteria: Know when ALND can be omitted (T1/T2, ≤2 positive SLNs, breast conservation with whole breast radiation) 1

7. Radiation indications: When is PMRT indicated after mastectomy?

8. Complications: Be able to discuss rates and risk factors for lymphedema

Remember that surgical management of breast cancer continues to evolve toward less invasive approaches when oncologically safe, with the goal of reducing morbidity while maintaining excellent outcomes.