Is sentinel lymph node biopsy recommended for clinically node‑negative early‑stage breast cancer or cutaneous melanoma, and how should positive versus negative results be managed?

Sentinel Lymph Node Biopsy in Early-Stage Breast Cancer and Melanoma

Sentinel lymph node biopsy (SLNB) is the standard of care for axillary staging in clinically node-negative early-stage breast cancer (T1-T2, stages I-II) and should be performed in melanoma patients with tumors >1.0 mm thick or ≤1.0 mm with ulceration. 1, 2

Breast Cancer: When to Perform SLNB

Clear Indications

• Perform SLNB in all patients with T1-T2 invasive breast cancer (≤5 cm) who have clinically negative axillary nodes confirmed by both physical examination and negative preoperative axillary ultrasound. 2, 3
• Both breast-conserving surgery and mastectomy patients are appropriate candidates. 2
• The procedure must only be performed by surgeons with demonstrated false-negative rates <10% and successful mapping rates >90%. 2, 3

Special Circumstances Where SLNB May Be Offered

SLNB can be performed in select patients with: 1

• Multicentric tumors (moderate strength recommendation)
• DCIS when mastectomy is performed
• Prior breast and/or axillary surgery
• After preoperative/neoadjuvant systemic therapy (though false-negative rates are higher at 10-30%, requiring removal of at least 2 SLNs) 3, 4

Absolute Contraindications to SLNB

Do not perform SLNB in patients with: 1

• Large or locally advanced invasive breast cancer (T3/T4 tumors)
• Inflammatory breast cancer
• DCIS when breast-conserving surgery is planned
• Pregnancy
• Clinically suspicious or palpable axillary nodes 5

Emerging Exception: Omitting SLNB Entirely

SLNB may be omitted in highly select postmenopausal patients ≥50 years old with grade 1-2, small (≤2 cm), hormone receptor-positive, HER2-negative breast cancer undergoing breast-conserving therapy with negative preoperative axillary ultrasound. 5 However, multidisciplinary discussion of adjuvant therapy options must occur prior to surgery when omitting SLNB. 1

Management Based on SLNB Results in Breast Cancer

Negative SLNB

Patients with negative sentinel lymph nodes should NOT undergo completion axillary lymph node dissection (ALND). 1, 5 This is a strong recommendation based on high-quality evidence showing:

• No statistically significant differences in event-free survival or overall survival at 15-year follow-up between SLNB alone versus ALND 6
• 11.5% reduction in postsurgical complications compared to routine ALND 5
• Axillary recurrence rates of only 0-1.6% 3

Positive SLNB: 1-2 Metastatic Nodes

For breast-conserving surgery with whole-breast radiotherapy:

• Do NOT perform completion ALND in patients with 1-2 positive sentinel nodes. 1, 5 This strong recommendation is based on the ACOSOG Z0011 trial showing equivalent long-term survival without completion ALND. 5

For mastectomy:

• Offer post-mastectomy radiation with regional nodal irradiation as an alternative to completion ALND in patients with 1-2 positive sentinel nodes. 5 This approach results in significantly lower lymphedema rates compared to ALND. 5
• Alternatively, ALND may be offered (weak recommendation, low-quality evidence). 1

Positive SLNB: ≥3 Metastatic Nodes

Perform ALND followed by regional nodal irradiation in patients who receive mastectomy and have ≥3 positive sentinel nodes. 5 Note that patients with three positive nodes were underrepresented in trials evaluating omission of completion ALND. 1

Melanoma: SLNB Indications

Perform SLNB in melanoma patients with: 2, 3

• Stage IB or II disease (>1.0 mm thick or ≤1.0 mm with ulceration/Clark level IV-V)
• Discuss SLNB for stage IA thin melanomas (≤1.0 mm) with adverse features: thickness >0.75 mm, high mitotic rate, young patient age, positive deep margins, or lymphovascular invasion 2

Technical Requirements for Accuracy

Use dual technique with both radiotracer and blue dye to achieve the highest success rates and lowest false-negative rates. 2, 3 This approach achieves identification rates >95% when performed by experienced surgeons. 3

Pathologic processing requires: 3

• Slicing nodes no thicker than 2.0 mm
• Examining at least one section from each block
• Quantifying nodal tumor burden as part of standard analysis 3

Critical Pitfalls to Avoid

1. Do not perform SLNB before neoadjuvant therapy, even in clinically node-negative patients, as this compromises the ability to assess treatment response. 2

2. Do not rely on clinical examination alone—ultrasound must be used to identify occult nodal disease in clinically node-negative patients. 2, 3

3. Do not default to ALND based solely on imaging findings of suspicious nodes without pathologic confirmation. 5

4. Do not routinely use immunohistochemistry (IHC) for detection of isolated tumor cells or micrometastases, as neither the NSABP B32 nor ACOSOG Z0010 trials support routine use of multiple levels or IHC for detection of occult metastases. 3 There is no significant difference in 5-year overall survival or disease-free survival between patients with and without IHC-detected occult metastases. 3