Development and Validation of a Modified Pathologic Nodal Classification System for Cutaneous Melanoma

Area of Science:

• Oncology
• Dermatology
• Surgical Pathology

Background:

• Current nodal staging for cutaneous melanoma may not accurately reflect prognosis due to evolving evaluation methods.
• Existing systems were developed for completion lymph node dissection (CLND) and do not consistently show increasing mortality with higher nodal burden.

Purpose of the Study:

• To develop and validate a modified nodal classification system for cutaneous melanoma.
• To improve the accuracy of melanoma staging and patient risk stratification.

Main Methods:

• Retrospective cohort analysis of 105,785 patients with cutaneous melanoma from the National Cancer Database (2004-2015).
• Development of a modified nodal classification system using recursive partitioning analysis (RPA) based on number of positive lymph nodes, clinically detected metastases, and in-transit metastases.
• Validation in 85,499 patients from the Surveillance, Epidemiology, and End Results (SEER-18) database.

Main Results:

• The modified system demonstrated continuously increasing mortality across its proposed lymph node classification groups.
• The current American Joint Committee on Cancer (AJCC) nodal classification system showed a less consistent mortality profile.
• The proposed system accurately stratified patients, even when excluding those undergoing CLND for microscopic metastases, and was validated for overall survival and cause-specific mortality.

Conclusions:

• A modified nodal classification system offers improved accuracy in stratifying mortality risk for cutaneous melanoma.
• This system is particularly relevant given the increasing use of sentinel lymph node biopsy without CLND.
• The proposed system should be considered for future melanoma staging guidelines to enhance prognostic accuracy.