Treatment of Melanoma with Breslow Thickness 1-2 mm
For melanoma with Breslow thickness of 1-2 mm, perform wide local excision with a 1 cm surgical margin and strongly consider sentinel lymph node biopsy for accurate staging. 1
Surgical Excision
The primary treatment is wide local excision with a 1 cm margin for all melanomas up to 2 mm in thickness. 1 This recommendation is based on Level II evidence from the most recent ESMO guidelines (2019) and represents a consensus across multiple international guidelines. 1
The 1 cm margin applies to the entire 1-2 mm thickness range and has been validated in multiple randomized trials showing equivalent survival and local recurrence rates compared to wider margins. 1, 2
Modifications with reduced margins are acceptable for preservation of function in acral (hands/feet) and facial melanomas, though prospective randomized trial data are lacking for these anatomic sites. 1
Critical pitfall: Clinical/surgical margins do not equal histologic margins—meticulous pathological confirmation of clear margins is essential. 2, 3
Sentinel Lymph Node Biopsy (SLNB)
SLNB is strongly recommended for melanomas 1-2 mm thick for accurate staging, though it provides prognostic information rather than therapeutic benefit. 1
The MSLT-I trial demonstrated that SLNB validates staging but showed no unequivocal survival benefit, meaning it should be considered a staging procedure rather than therapeutic intervention. 1
SLNB should only be performed in experienced centers with specific quality criteria including simultaneous performance with wide excision to avoid lymphatic drainage modifications. 1
Within the 1-2 mm range, there is significant biological heterogeneity: tumors 1.0-1.59 mm have an 8.7% sentinel node positivity rate versus 19.3% for tumors 1.6-2.0 mm. 4
Additional high-risk features that increase the likelihood of positive SLNB include: lymphovascular invasion, younger age, and ulceration. 4
When SLNB May Be Omitted
A small subgroup of patients with tumors <1.6 mm, no lymphovascular invasion, and age ≥59 years have only a 5% risk of positive sentinel nodes, though current guidelines still recommend SLNB for most patients in this thickness range. 4
What NOT to Do
Do not perform elective complete lymph node dissection or prophylactic lymph node irradiation. 1 This is associated with significant morbidity (10-15% early complications, 6-15% late lymphedema in lower limbs) without survival benefit. 1
Special Considerations
For lentigo maligna melanoma subtype in this thickness range, wider margins or specialized techniques may be necessary due to characteristic subclinical extension. 2, 3
If tumor regression is present on histology, consider using margins for the next thickness category (2 cm) as regression may underestimate true tumor burden. 1, 2
The presence of ulceration, higher mitotic rate, and specific histologic subtypes (desmoplastic, acral) are associated with worse prognosis and should be documented for risk stratification. 4, 5
Adjuvant Therapy
There is no standard adjuvant therapy recommended for completely resected stage IB-IIA melanoma (which includes most 1-2 mm tumors without nodal involvement). 1 Adjuvant interferon has shown disease-free survival benefit in some trials but remains controversial and should only be considered in the context of clinical trials or for high-risk features. 1