Abstract

Introduction: Sentinel lymph node biopsy (SLNB) is a routine surgical procedure for the management of melanomas greater than 0.8 mm in thickness or with ulceration, and other solid tumor malignancies. Currently, College of American Pathologists (CAP) guidelines have a recommended maximum number of lymph nodes which are considered “sentinel” for invasive breast carcinoma, but this does not exist for melanoma. Design: In this multi-institutional Canadian study, we retrospectively quantified total lymph node yields for melanoma SLNB procedures from August 1, 2021 to July 31, 2022 with some interval variation. Positivity rate, immunohistochemical protocols, cost analysis, and local practice variability were also evaluated. Cases were grouped into G1 if the total sentinel lymph node count was one and G>1 if there were more, and analyzed. Results: There were 708 cases evaluated in the 2-year period across all institutions. The average number of sentinel lymph nodes collected by surgeons per SLNB was 2.41 (standard deviation: 1.90). The rate of sentinel lymph node positivity was not significantly different between the two analyzed groups (p=0.09) with a range of positivity across institutions. Surgical techniques for SLNB were similar between institutions. Additionally, costs varied but, universally, additional sampled lymph nodes incurred additional costs from reflex immunohistochemistry, and pathologist/technologist time. Conclusion: The lack of standardized sentinel lymph node practice for melanoma leads to 1.) variability in surgical and pathology practices 2.) differential laboratory resource utilization and associated costs, and 3.) non-standardized, center-dependent protocols. Our study supports a need in establishing national guidelines for SNLB specimens.