From the Guidelines
Surgical excision with complete circumferential peripheral and deep margin assessment (CCPDMA) is the recommended treatment for acral melanoma, particularly for lentigo maligna (LM) and acral lentiginous types, with surgical margins of at least 0.5 cm. Acral melanoma is a rare subtype of melanoma that occurs on the palms, soles, or under the nails, and it's the most common form of melanoma in people with darker skin tones, though it can affect anyone [ 1 ]. For diagnosis, a dermatologist should perform a thorough examination and biopsy of suspicious lesions.
Treatment Options
- Surgical excision with appropriate margins based on tumor thickness is the primary treatment for acral melanoma [ 1 ].
- Sentinel lymph node biopsy may be recommended for tumors thicker than 1mm.
- For advanced cases, systemic therapies including immunotherapy (such as pembrolizumab or nivolumab) or targeted therapy (for BRAF-mutated tumors) may be necessary.
- Mohs micrographic surgery (MMS) and staged excision with formalin-fixed, paraffin-embedded (ie, permanent) sections are types of CCPDMA that may be considered selectively for MIS (LM and acral lentiginous types) and for minimally invasive (T1a) LM melanoma in anatomically constrained areas [ 1 ].
Prognosis and Follow-up
- The prognosis depends on tumor thickness and stage at diagnosis, with early detection significantly improving outcomes.
- Acral melanoma differs from other melanoma types in its location and molecular profile, often lacking BRAF mutations common in other melanomas, which can affect treatment options [ 1 ].
- Regular follow-up with dermatologists is essential after treatment to monitor for recurrence.
- Regular skin self-examinations focusing on palms, soles, and nail beds are crucial for early detection, as acral melanoma often goes unnoticed until later stages.
From the Research
Characteristics of Acral Melanoma
- Acral melanoma is a rare subtype of melanoma with unique histologic and biologic characteristics 2
- It appears in the palms, soles, and nails, and is often considered different from other cutaneous melanomas 3
- Acral melanoma is very rare in Caucasian populations and is often not included in genetic analysis and clinical trials 3
Treatment and Surgical Margins
- The appropriate size of resection margins in acral melanoma is not clearly established 4
- A study found that a 2 cm margin was associated with a reduced rate of local recurrence and in-transit recurrence compared with a <2 cm margin for thick acral melanoma 5
- However, another study found that a resection margin of 1 to 2 cm did not affect tumor recurrence or survival in patients with acral melanoma 4
- Narrow-margin excision may be acceptable for acral melanoma, but further studies are needed to determine the optimal surgical margin 6
Prognosis and Survival
- The mortality rates of patients with T1-3 melanomas were similar regardless of the excision margins, but patients with T4 melanoma treated with narrow-margin excision had a higher mortality rate 6
- Breslow thickness was found to be an independent risk factor for melanoma-specific survival and disease-free survival 6
- Factors associated with survival in patients with acral melanoma include Breslow index, ulceration, advanced clinical stage, and use of adjuvant therapy 4
Future Directions
- Further studies are needed to evaluate the efficacy of systemic immune and targeted molecular therapies for advanced acral melanoma 2
- Genetic analyses have shown that acral melanoma carries a sufficient mutational load and neoantigen formation to be targeted by the immune system, arguing for a potential benefit with novel immunotherapeutic strategies 3