878 The prognostic value of tumor infiltrating lymphocytes in vulvovaginal melanoma

Introduction/Background Vulvovaginal melanoma is a rare form of cancer, accounting for 1–2% of melanomas in women. Prognosis is poor, with a high frequency of metastatic forms at diagnosis and a median survival rate of 9 to 53 months. Immunotherapy has shown promising results in cutaneous melanoma, but response rates in vulvovaginal melanoma are much lower, indicating a different immune microenvironment. Aim of this study was to assess the relation between immune microenvironment, survival, and clinico-pathological characteristics Methodology 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, as well as NGS analysis when feasible Results 42 patients were selected during the study period, but 13 were finally excluded due to unavailable FFPE material or unknown follow-up data. 12 cases (63,2%) had at least one genetic mutation, 3 (16,7%) had BRAF, 3 (16,7%) had c-KIT mutation and 4 (23,5%) had NRAS mutations. High stromal tumor infiltrating lymphocytes (sTILs) was identified in 13 patients (46.4%), and brisk 15 TILs in 17 patients (60.7%). sTILs density higher than 40% and brisk distribution were the single clinico-pathologic factor associated with increased disease-free survival. Conclusion The study results highlight the potential of brisk TILs and sTILs as a marker for disease progression, and for response to immunotherapy strategies. Further research is needed to confirm these results. Disclosures No disclosure to report.