What is the treatment for subungual melanoma?

Treatment of Subungual Melanoma

Subungual melanoma should be treated with amputation at the distal interphalangeal joint for fingers or metatarsophalangeal joint for toes, as this approach provides the best balance of oncologic control and functional outcomes. 1

Diagnosis and Initial Assessment

• Suspicious features requiring investigation:

  • Color heterogeneity (multiple colors within pigmented band)
  • Nail bed changes (ulceration or nodule formation)
  • Onycholysis (separation of nail from nail bed) 2
  • Longitudinal pigmented stripe under the nail plate 3

• Diagnostic approach:

  • Full-thickness biopsy is mandatory for accurate diagnosis
  • The nail should be removed and the nail matrix adequately sampled 1
  • Biopsies should be performed by surgeons experienced with nail procedures 2

Surgical Management Options

Standard Approach: Amputation

• Amputation at the distal interphalangeal joint for fingers and metatarsophalangeal joint for toes is recommended 1
• This approach has demonstrated no local recurrences in clinical studies 1
• Distal phalangeal amputation with a margin of normal-appearing skin is an alternative approach 1

Conservative Approaches

• Conservative surgery (non-amputative wide excision with skin grafting) may be considered for:

  • In situ melanoma
  • Minimally invasive subungual melanoma 4

• However, functional results of nail bed excision with skin grafting are often suboptimal:

  • Patients frequently report persistent sensitivity to light touch
  • Troubling pain with minor trauma 1
  • Undertreatment of early disease is associated with local recurrence 5

Considerations for Surgical Approach

Factors favoring amputation:

• More advanced disease (thicker tumors)
• Toe lesions (tend to be thicker than finger lesions, with poorer prognosis) 5
• Need for definitive treatment with minimal risk of recurrence

Factors potentially supporting conservative approach:

• In situ or very thin melanoma
• Strong patient preference for digit preservation
• Histopathological evidence suggesting nail matrix area tends to be more resistant to invasion 6

Prognostic Factors

• Breslow thickness significantly impacts prognosis:

  • Patients with lesions ≤1.0 mm have better survival rates 7
  • Toe lesions tend to be thicker than finger lesions (mean 3.5 vs 2.5 mm) 5
  • 5-year overall survival: 40% for toe lesions vs 72% for finger lesions 5

• Ulceration status affects survival:

  • Estimated 5-year survival rate: 39% for ulcerated lesions vs 80% for non-ulcerated lesions 7

Staging and Follow-up

• Sentinel lymph node biopsy should be considered for invasive subungual melanoma

  • Positive sentinel nodes are associated with poorer outcomes 5

• Follow-up should include:

  • Physical examination with attention to regional lymph nodes
  • Appropriate imaging based on stage of disease 1

Common Pitfalls

• Delayed diagnosis due to misdiagnosis as onychomycosis or other benign nail conditions 2
• Inadequate biopsy sampling leading to underestimation of invasion depth 2
• Undertreatment of early disease, which can lead to local recurrence 5
• Attempting conservative approaches without appropriate patient selection

While there is a trend toward more conservative approaches for early subungual melanoma, the current evidence still supports amputation as the standard of care for most cases, particularly for invasive disease, to ensure optimal oncologic outcomes.