Sentinel lymph node positivity more likely in younger patients with T1a melanomas

Among patients with T1a cutaneous melanomas, younger age and tumors in the head/neck region were most likely to demonstrate sentinel lymph node positivity, according to a study.

“Sentinel lymph node biopsy is not routinely recommended for T1a cutaneous melanoma due to the overall low risk of positivity,” Adrienne B. Shannon, MD, of the division of endocrine and oncologic surgery at the Hospital of the University of Pennsylvania in Philadelphia, and colleagues wrote. “Prognostic factors for SLN positivity in this population are poorly characterized.”

The multi-center cohort study included 965 patients with T1a melanoma from five high-volume centers between 2001 and 2020 Eligible patients had non-ulcerated cutaneous melanoma measuring less than 0.8 mm and were treated with wide local excision with sentinel lymph node biopsy. The patients were dichotomized by age into those aged 42 years and younger and those aged older than 42 years.

Overall, 43 patients (4.4%) were SLN positive.

Factors associated with SLN positivity included age of 42 years and younger vs. age older than 42 years (7.5% vs. 3.7%), a primary tumor location of the head/neck vs. other locations (9.2% vs. 4%), and those with vs. without lymphovascular invasion (21.4% vs. 4.2%).

Patients with two or more mitoses per square millimeter were also more likely than those without to experience SLN positivity (8.2% vs. 3.4%). An SLN positivity rate of 18.4% was reported for patients aged less than 42 years with two or more mitoses per square millimeter.

The retrospective nature of the analysis may limit the applicability of the results, according to the researchers.

“SLN [positivity] is low in patients with T1a melanomas, but younger age, [lymphovascular invasion], mitogenicity, and head/neck primary site appear to confer a higher risk of SLN [positivity],” the researchers wrote.