From the Guidelines
The risk of regional node metastasis in a 0.70 mm thick melanoma is less than 5% (Answer A). Melanoma thickness, measured by Breslow depth, is one of the most important prognostic factors for predicting metastatic potential. Thin melanomas, particularly those less than 0.8 mm in thickness, have a very low risk of spreading to regional lymph nodes. This is why sentinel lymph node biopsy is typically not recommended as a routine procedure for melanomas less than 0.8 mm thick unless there are other adverse features present (such as ulceration, high mitotic rate, or lymphovascular invasion) 1. The risk increases significantly with greater tumor thickness, with melanomas greater than 1 mm having substantially higher rates of nodal metastasis. Some key points to consider include:
- The overall rate of sentinel node metastases in thin melanoma is estimated to be approximately 5.2% 1.
- For patients with lesions > 0.8 mm in thickness, the incidence is approximately 8% 1.
- Breslow thickness ≥ 0.75 mm, Clark level ≥ IV, and ≥ 1 mitoses/mm² are variables that are associated with higher rates of SLN positivity 1.
- Ulceration is an additional potential factor associated with higher risk 1.
- The NCCN guidelines recommend that SLNB should not be performed if a patient’s risk of a positive SLN is <5% (ie, T1a melanoma), but should be discussed and considered if the risk is 5%–10% (ie, T1b melanoma), and should be discussed and offered if the probability of a positive SLN is >10% (T2a-T4b melanoma) 1. Given the information from the most recent and highest quality study 1, the risk of regional node metastasis in a 0.70 mm thick melanoma is indeed less than 5%.
From the Research
Risk of Regional Node Metastasis in 0.70 mm Thick Melanoma
- The risk of regional node metastasis in 0.70 mm thick melanoma is not directly stated in the provided studies.
- However, according to the study 2, routine SLN biopsy is not recommended for patients with thin melanomas that are T1a (non-ulcerated lesions < 0.8 mm in Breslow thickness).
- The study 3 suggests that a mitotic rate ≥ 4 is significant for SLN positivity in thin melanomas.
- The study 4 recommends discussing sentinel lymph node biopsy for melanomas ≥ 1 mm thickness (≥ 0.8 mm if other high-risk features).
- The study 5 states that lesions with a Breslow depth greater than 0.8 mm may need further diagnostic tests or procedures, including sentinel lymph node biopsy.
- The study 6 found that thin nodular primary melanomas (T1 ≤ 1.0 mm) are more likely to have regional metastasis compared to superficial spreading melanoma.
- Based on the provided studies, it can be inferred that the risk of regional node metastasis in 0.70 mm thick melanoma is likely less than 5% to 10%, but the exact percentage is not specified 2, 3, 4, 5, 6.