What is the recommended treatment and prognosis for a patient with stage I acral melanoma (tumor ≤2 cm, no ulceration, no clinically evident nodal or distant disease)?

Treatment and Prognosis for Stage I Acral Melanoma

For stage I acral melanoma (≤2 cm, non-ulcerated), perform wide excision with 1 cm margins for tumors ≤1 mm thick or 1-2 cm margins for tumors 1-2 mm thick, discuss sentinel lymph node biopsy for tumors ≥0.8 mm, and counsel patients that acral melanomas carry approximately twice the risk of recurrence and death compared to non-acral melanomas of equivalent stage. 1, 2, 3

Surgical Management

Primary Tumor Excision

• For tumors ≤1 mm thick (T1): Wide excision with 1 cm surgical margins is the standard of care 1

• For tumors 1.01-2.0 mm thick (T2): Wide excision with 1-2 cm margins is recommended, with the specific margin determined by anatomic location and functional considerations 1, 4

• Critical consideration for acral sites: Margins may need modification to preserve function, particularly for digit-sparing procedures, though margins <1 cm for invasive melanoma are generally not recommended until further studies are available 1

• Depth of excision: Should extend to (but not including) the fascia 1

Sentinel Lymph Node Biopsy (SLNB)

The decision regarding SLNB follows a risk-stratified approach:

• Not recommended: For melanoma in situ or T1a melanoma (≤0.8 mm without ulceration) 1

• Discussion warranted: For T1b melanoma (≤0.8 mm with ulceration, or 0.8-1.0 mm with or without ulceration) 1

• Strongly recommended: For all melanomas >1 mm thickness (T2a and above), which provides critical staging information 1

• Timing is critical: SLNB should be performed before or concomitant with wide excision during the same operative setting to minimize disruption of lymphatic channels and optimize accuracy 1

• Important caveat: While SLNB provides prognostic information, it has not demonstrated overall survival benefit and should be discussed as primarily a staging procedure 1

Prognosis: The Acral Melanoma Disadvantage

Comparative Survival Data

Acral melanomas demonstrate significantly worse outcomes than non-acral cutaneous melanomas when matched for stage:

• Hazard ratio for death: 1.8 (95% CI 1.2-2.7) compared to extremity non-acral melanomas of equivalent stage 2

• Recurrence rates: 49% for acral melanoma vs. 30% for non-acral melanoma at equivalent stages 3

• Locoregional recurrence: Nearly double the rate in acral melanoma compared to non-acral melanoma (p=0.001) 3

Stage-Specific Prognostic Factors

The following factors independently predict worse disease-specific survival in acral melanoma:

• Breslow thickness (p<0.001) 2
• Ulceration (p<0.001) 2
• Positive sentinel lymph node (p<0.001) 2
• Pathologic stage (p<0.001) 2

Thickness-Specific Recurrence Patterns

For tumors <2 mm thick: Acral melanomas show significantly higher recurrence rates compared to non-acral melanomas (p=0.048), suggesting these tumors may be biologically more aggressive even at thinner depths 3

For tumors ≥2 mm thick: The difference in recurrence rates between acral and non-acral melanomas becomes less pronounced (p=0.12), though still clinically significant 3

Critical Pitfalls and How to Avoid Them

Inadequate Surgical Margins

• Acral melanomas have higher locoregional recurrence rates, raising questions about whether standard margin recommendations are sufficient 3

• While current guidelines recommend 1 cm margins for tumors ≤1 mm, some evidence suggests acral melanomas <2 mm may require more aggressive surgical treatment 3

• Never use margins <1 cm for invasive acral melanoma outside of clinical trials, as this is associated with increased recurrence risk 1

Delayed or Inadequate Staging

• Always perform complete physical examination including all regional lymph node basins, as acral melanomas have higher rates of nodal involvement 1

• For stage I disease with no palpable nodes, routine imaging is not necessary for T1a lesions, but consider baseline imaging for T1b and T2 lesions given the aggressive biology of acral melanomas 1

Underestimating Biological Aggressiveness

• Counsel patients that acral melanoma is not simply "melanoma on the foot/hand" but represents a distinct biological entity with worse prognosis 2, 3

• The inferior survival of acral melanoma compared to non-acral melanoma at equivalent stages likely reflects inherent alterations in tumor biology, not just delayed diagnosis 2

• Consider more aggressive surveillance protocols for acral melanoma patients compared to non-acral melanoma of equivalent stage, given the doubled locoregional recurrence rate 3

Functional Preservation vs. Oncologic Adequacy

• While digit-sparing surgery is desirable, amputation may be necessary for tumors on digits or midfoot where adequate margins cannot be achieved while preserving function 5

• The balance between cosmesis/function and oncologic adequacy is particularly challenging in acral sites, but oncologic principles should not be compromised 1

Adjuvant Therapy Considerations

• No standard adjuvant therapy exists for stage I melanoma 1

• Adjuvant interferon therapy has shown disease-free survival benefit in higher-risk patients but not overall survival benefit, and should only be considered in the context of clinical trials for stage I disease 1

• Radiotherapy is not indicated for completely excised stage I melanoma with clear margins 1