From the Guidelines
Sentinel lymph node biopsy is recommended for patients with melanoma who have a primary tumor thickness greater than 0.8 mm, as well as for those with thinner melanomas (0.8 mm or less) that have concerning features such as ulceration, high mitotic rate, or lymphovascular invasion, as it provides important prognostic information and helps guide subsequent management decisions 1, 2.
Indications for Sentinel Lymph Node Biopsy
The indications for sentinel lymph node biopsy in melanoma include:
- Intermediate-thickness melanomas (T2 or T3, Breslow thickness of > 1.0 to 4.0 mm), where SLN biopsy is recommended due to the potential benefits of accurate staging and decreased rates of recurrence in regional nodes 1.
- Thick melanomas (T4, > 4.0 mm in Breslow thickness), where SLN biopsy may be recommended after a thorough discussion with the patient of the potential benefits and risks of harm associated with the procedure 2.
- Thin melanomas (T1b, 0.8 to 1.0 mm Breslow thickness or 0.8 mm Breslow thickness with ulceration), where SLN biopsy may be considered after a thorough discussion with the patient of the potential benefits and risks of harm associated with the procedure 2.
Rationale and Procedure
The rationale behind SLNB is that it provides important prognostic information by identifying microscopic nodal metastases, which helps guide subsequent management decisions including the need for completion lymph node dissection, adjuvant therapy, or more intensive surveillance 1. The procedure involves injecting a radioactive tracer and/or blue dye near the primary tumor site, which then travels through lymphatic channels to identify the first draining lymph node(s) 1.
Considerations
SLNB is not typically recommended for very thin melanomas (less than 0.8 mm without concerning features) due to the low risk of nodal metastasis, nor for patients with clinically evident nodal disease who should instead undergo complete lymph node dissection 2. The decision to perform SLNB should be made on a case-by-case basis, taking into account the individual patient's risk factors and the potential benefits and risks of the procedure 1, 2.
From the Research
Indications for Sentinel Lymph Node Biopsy in Melanoma
- Sentinel lymph node (SLN) biopsy is recommended for patients with intermediate-thickness melanomas (T2 or T3; Breslow thickness of >1.0 to 4.0 mm) 3, 4.
- For patients with thin melanomas (T1a), routine SLN biopsy is not recommended, but it may be considered for those with T1b melanomas (0.8 to 1.0 mm Breslow thickness or <0.8 mm Breslow thickness with ulceration) after a thorough discussion of the potential benefits and risks 3, 5.
- SLN biopsy may be recommended for patients with thick melanomas (T4; > 4.0 mm in Breslow thickness), but this should be done after discussing the potential benefits and risks with the patient 3, 4.
- The decision to perform SLN biopsy should take into account the patient's overall health, the presence of ulceration, and other clinicopathological factors 3, 6.
Special Considerations
- For patients with a positive SLN biopsy, completion lymph node dissection (CLND) or careful observation are options, depending on the patient's risk factors and the presence of micrometastatic disease 3, 5.
- The role of SLN biopsy in the era of modern adjuvant systemic therapy with immune checkpoint inhibition (ICI) or targeted therapies (TT) is evolving, and its use may decrease in the future as biomarkers and other staging methods become more widely available 7.
- Emerging biomarkers, such as gene expression profilers (GEP), immunohistological signatures, and liquid biopsies with ctDNA, may reduce the need for SLN biopsy staging in the upcoming decade 7.