Abstract 4564: Tumor infiltrating lymphocytes are associated with p16 protein expression in acral lentiginous melanoma

Abstract Background: The loss of function of gene p16(INK4a)/CDKN2 is associated with the development of several neoplasm and tumor progression, likewise, the level of tumor infiltrating lymphocytes is a predictive and prognostic biomarker of survival. This study aims to evaluate the association between composition of tumor infiltrating lymphocytes (TILs) and expression of p16 in acral lentiginous melanoma (ALM), and their impact on prognosis. Materials and methods: A cohort of 148 surgical pathology specimens of ALM was studied. TILs were evaluated by immunohistochemical detection of CD3 and CD8, along with CD20, CD4, CD68, and CD163 in a subset of 43 cases, likewise, we classify the level of TILs in grades by combining density and distribution. p16 protein expression by immunohistochemistry was also investigated in all cases. Results: The median age was 66 years, median Breslow thickness was 6.0 mm, Grade III of TILs was found in 28.4% and lymph nodes were involved in 44.6%. Breslow thickness (p<0.001), stage I-II (p<0.001), negative lymph nodes (p<0.001) and <10% p16 (p<0.001) were associated with longer survival. Grade III of TILs was associated with thinner Breslow thickness (p=0.008) and lower mitosis (p=0.047). A higher density of CD3 TILs was associated with male gender (p=0.008), thinner Breslow thickness (p=0.047), negative lymph node (p=0.031), early stage (p=0.046), and p16 nuclear expression of >10% (p=0.045). Higher CD8 TIL was associated with >p16 (p=0.03). Survival analysis found that longer survival doesn’t associated with high grade of TILs (p=0.094). Levels of CD3+ and CD8+ cells were correlated with those of CD4+, CD20+, CD68+ and CD163+ immune cells. Conclusions: Loss of expression of p16 is associated with lower levels of CD3+ and CD8+ TIL, indicating a probable relationship between p16 and TILs immune response in ALM. Citation Format: Marco A. Galvez Nino, Miluska Castillo, Luis A. Bernabe, sandro Casavilca, Valeria Villegas, Joselyn Sanchez, Jorge Dunstan, Julio Abugatas, Carlos Castaneda, Henry Gomez. Tumor infiltrating lymphocytes are associated with p16 protein expression in acral lentiginous melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4564.