Objective To assess the relation between immune microenvironment, survival, and clinicopathological characteristics.

Methods This study was a retrospective, single-center, observational study. Patients with a vulvovaginal melanoma and available archived material were included. All cases underwent pathology review, tumor-infiltrating lymphocyte quantification, and next-generation sequencing analysis, when feasible. Clinical data included demographic, treatment, and prognostic data.

Results Forty-two patients were selected during the study period, but 13 were finally excluded owing to unavailable formalin-fixed, paraffin-embedded material or unknown follow-up data. Twelve of 19 cases (63.2%) had at least one genetic mutation, 3/18 (16.7%) had BRAF, 3/18 (16.7%) had c-KIT mutation, and 4/17 (23.5%) had NRAS mutations. High stromal tumor-infiltrating lymphocytes were identified in 13/28 patients (46.4%), and brisk tumor-infiltrating lymphocytes in 17/28 patients (60.7%). A density of stromal tumor-infiltrating lymphocytes >40% and brisk distribution were the single clinicopathologic factor associated with increased disease-free survival.

Conclusion The study showed that brisk tumor-infiltrating lymphocytes and stromal tumor-infiltrating lymphocytes were a marker for disease progression, and for response to immunotherapy strategies. To validate these findings on a larger scale, further research is warranted through a multicenter study with a larger cohort and additional genetic and translational analysis.