The Risk of Regional Lymph Node Metastases in Patients with Melanoma Less Than 1.0 Mm Thick: Recommendations for Sentinel Lymph Node Biopsy

BACKGROUND: Lymphatic mapping and sentinel lymph node biopsy can upstage patients with intermediate thickness (1.0 to 4.0 mm) melanoma. Currently, there are no strict guidelines for sentinel lymph node biopsy in patients with melanoma <1.0 mm thick. STUDY DESIGN: A retrospective review of our patient database (598 patients treated at two institutions in Baltimore, MD, between January 1970 and June 2002) was performed to identify patients with primary cutaneous melanoma <1.0 mm thick who developed recurrent disease. This cohort of patients with > or =5 years of followup from the date of diagnosis was compared with patients with primary melanoma of similar thickness and similar followup intervals without recurrent disease. RESULTS: A total of 114 patients with primary cutaneous melanoma <1.0 mm thick were identified, 17 of whom developed disease recurrence. In 13 patients, the site of first recurrence was the regional lymph nodes and in 4 patients disease recurred with distant metastases. The median time to lymph node recurrence was 55 months (range 2 to 112) months. Patients with regional lymph node recurrences had a significant (p = 0.02) difference in median primary tumor thickness of 0.80 mm versus 0.45 mm in patients without recurrent disease; there was no association of Clark level of invasion to recurrence (p = 0.42). In all, 35% of patients (7 of 20) presenting with melanoma 0.80 to 0.99 mm thick developed lymph node recurrence a median of 41 months (range 8 to 112 months) after surgical treatment. CONCLUSIONS: Sentinel lymph node biopsy can be justified for patients with melanoma > or =0.8 mm thick provided that the technique would detect metastatic disease years before it becomes clinically evident.