Metastatic melanoma cells in the sentinel node cannot be ignored.

Area of Science:

• Oncology
• Surgical Pathology
• Melanoma Research

Background:

• Risk stratification for metastatic melanoma in sentinel nodes (SN) remains controversial.
• Submicrometastatic disease (<0.1 mm tumor burden) is debated as a distinct classification.
• The study hypothesizes that any melanoma cells in SNs indicate potentially life-threatening disease.

Purpose of the Study:

• To determine if submicrometastatic melanoma in sentinel nodes impacts patient prognosis.
• To evaluate the recurrence risk associated with varying tumor burdens in SNs.
• To challenge the classification of submicrometastatic disease as non-life-threatening.

Main Methods:

• Retrospective review of a prospectively maintained melanoma database (>1,100 patients).
• Inclusion criteria: invasive melanoma, SN biopsy, and ≥1 year follow-up.
• Patients categorized by SN tumor burden: node-negative, <0.1 mm, 0.1–1.0 mm, >1.0 mm; analyzed using Jonckheere-Terpstra, Fisher's exact, and Kaplan-Meier methods.

Main Results:

• 578 patients with invasive melanoma underwent SN procedures (July 1998–July 2007); median follow-up was 2.2 years.
• Statistically significant difference in recurrence rates between node-negative (11%) and <0.1 mm (24%) groups (p=0.049).
• Submicrometastatic group showed statistically significant earlier recurrence than node-negative group (p=0.048).

Conclusions:

• Submicrometastatic SN disease represents biologically aggressive melanoma with faster recurrence.
• Patients with submicrometastatic SN disease should not be treated as node-negative.
• Findings contradict proposals to spare completion node dissection for minimal SN tumor burden.