What is the best next step in managing a patient with a newly diagnosed melanoma less than 1 mm in thickness?

Management of Melanoma <1 mm in Thickness

The best next step for a 32-year-old woman with a newly diagnosed melanoma less than 1 mm in thickness is wide excision with a 1 cm margin. 1

Surgical Management Algorithm

1. Wide Local Excision (WLE)

   • For melanomas <1 mm in thickness: 1 cm margin 1, 2
   • This is a category 1 recommendation (highest level of evidence) 1
   • Modifications may be needed for preservation of function in anatomically sensitive areas such as fingers, toes, face, or ears 1

2. Sentinel Lymph Node Biopsy (SLNB)

   • SLNB is generally not necessary for melanomas <1 mm in thickness without other high-risk features 1, 2
   • According to ESMO guidelines, "In low-risk melanomas (tumor thickness <1 mm) no other investigations are necessary" 1
   • SLNB provides staging information but has not been shown to improve overall survival 1

Evidence Strength and Considerations

The recommendation for a 1 cm excision margin for melanomas <1 mm thick is consistently supported across multiple high-quality guidelines:

• The National Comprehensive Cancer Network (NCCN) recommends a 1 cm margin as a category 1 recommendation 1
• European Society for Medical Oncology (ESMO) guidelines recommend a 1 cm margin for tumors up to 2 mm in thickness 1
• British guidelines similarly recommend a 1 cm margin for melanomas ≤1 mm thick 1

Safety and Efficacy

The safety of conservative margins for thin melanomas is well-established:

• In a review of 1,151 consecutive patients with melanomas less than 1 mm thick, only one local recurrence was observed, even though 62% of these patients had resection margins of 2 cm or less 3
• Local recurrence rates for tumors less than 0.76 mm thick are extremely low (0.2% at 5 years) 3

Important Caveats

• Ensure complete histological clearance of margins
• Consider anatomic location when planning excision, as modifications may be needed for functional or cosmetic reasons
• While SLNB is generally not indicated for melanomas <1 mm, it may be considered if there are other high-risk features (such as ulceration, high mitotic rate, or lymphovascular invasion) 2
• Routine elective lymphadenectomy or elective irradiation to regional lymph nodes is not recommended 1

Follow-up Considerations

After appropriate surgical management with wide local excision:

• Regular clinical monitoring to detect potential relapse
• Patient education on sun protection and regular self-examination
• No indication for adjuvant therapy for thin melanomas without high-risk features 1

By following this evidence-based approach with appropriate surgical margins, the patient can expect excellent outcomes, as thin melanomas (<1 mm) generally have a very favorable prognosis when properly excised.