• Walter Rf Donica, Kyle R Stephens, Prejesh Philips, Kelly M McMasters, and Michael E Egger.
• The Hiram C. Polk Jr., MD Department of Surgery, University of Louisville, Louisville, KY.
• J. Am. Coll. Surg. 2025 Jan 23.

BackgroundThe definition of T1b cutaneous melanoma was changed in the 8th edition of the AJCC staging system based on survival differences but not risk of sentinel lymph node (SLN) metastases. We sought to evaluate changes in SLN biopsy (SLNB) use and rates of positive SLNB in response to updated staging criteria, and to evaluate the incidence of high-risk features in T1a melanoma in whom SLNB is now recommended.Study DesignThe 2021 National Cancer Database Melanoma PUF was used to obtain SLNB utilization and positivity rates in T1 (thin) melanoma (thickness ≤1.0mm) from 2012 to 2021. Rates were compared between AJCC 7th (2012-2017) and 8th editions (2018-2021). Factors associated with SLNB use in non-ulcerated T1 melanoma were evaluated. The presence of high-risk feature in T1a melanoma were identified and SLN positivity rates were reviewed.ResultsA total of 136,966 cases were included with 76,485 (55.8%) cases diagnosed under the AJCC 7th edition era (2021-2017). The overall proportion of patients with thin melanoma undergoing SLNB was relatively stable over the time periods, roughly 30%. In the AJCC 8th edition era, the overall SLNB positivity rate slightly increased from 4.5% to 6.6% (p < 0.001). There was increased SLNB use in melanoma with a thickness of 0.8 to 1.0mm (T1b: OR 2.53 [95% CI 2.31-2.78]) and decreased use when thickness was less than 0.8mm (T1a: OR 0.80 [0.76-0.85]). Rates of SLNB positivity increased in both thickness groups over time.ConclusionsAfter implementation of the AJCC 8th edition staging criteria, surgeons have become more selective in SLNB use with a resulting increase in SLNB positivity rate. Fewer SLNBs in T1a and more SLNBs in non-ulcerated T1b are being performed.Copyright © 2025 by the American College of Surgeons. Published by Wolters Kluwer Health, Inc. All rights reserved.

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