Management of Malignant Melanoma with Unknown Breslow Thickness and Negative Lymph Nodes
For malignant melanoma with unknown Breslow thickness that is node-negative, sentinel lymph node biopsy (SLNB) should be considered as a staging procedure in specialized skin cancer multidisciplinary teams, followed by appropriate wide local excision with margins determined by clinical assessment of the likely tumor thickness. 1
Surgical Management
Wide local excision is the primary treatment, with margins based on clinical assessment of the likely tumor thickness 1:
- For melanoma in situ: 0.5 cm margins
- For melanomas likely 1-2 mm thick: 1-2 cm margins
- For melanomas likely 2-4 mm thick: 2 cm margins
- For melanomas likely >4 mm thick: 2-3 cm margins
When Breslow thickness is unknown, clinical features such as ulceration, size, and appearance should guide margin decisions, with a minimum of 1 cm margin recommended for most cases 1
Sentinel Lymph Node Biopsy Considerations
Despite negative clinical nodes, SLNB should be considered for staging purposes, especially if the melanoma is suspected to be >1 mm in thickness based on clinical assessment 1
SLNB provides accurate staging information that can guide further management decisions and eligibility for adjuvant therapy 1
Patients should understand that SLNB is primarily a staging procedure without proven therapeutic value 1
The surgical risks of SLNB (approximately 5% morbidity), the possibility of failure to find a sentinel node, and potential false-negative results should be explained to patients 1
Imaging and Further Assessment
Baseline radiologic imaging is not recommended for asymptomatic patients with clinically node-negative melanoma 1
Imaging studies should be performed only to evaluate specific signs or symptoms of potential metastasis 1, 2
PET-CT is not useful for initial staging of clinically localized melanoma but may be considered if there are specific signs or symptoms of metastatic disease 2
Follow-up Recommendations
Regular clinical follow-up is recommended as the primary surveillance strategy 1
Ultrasound of the regional lymph node basin should be considered in cases where:
- The patient meets criteria for SLNB but does not undergo the procedure
- SLNB is not technically successful
- Expertise in nodal ultrasound surveillance is available 1
Special Considerations
If the melanoma is suspected to be very thin (<0.75 mm) based on clinical assessment, SLNB may not be necessary as the risk of nodal metastasis is low (approximately 5%) 3
For melanomas suspected to be thick (>4 mm), SLNB should be strongly considered as these have up to 39% risk of positive sentinel nodes and SLNB provides important staging information 4, 1
Elective lymph node dissection is not recommended in the absence of clinically evident nodal disease 1
In cases where SLNB reveals positive nodes, completion lymph node dissection should be considered 1
Adjuvant Therapy Considerations
Adjuvant therapy decisions should be based on final pathologic staging after surgery 5
For patients with high-risk features after complete staging, adjuvant immunotherapy with agents such as nivolumab may be considered 5
Clinical trials should be considered for eligible patients, particularly those with higher-risk features 1