Prognostic role of tumoral PDL1 expression and peritumoral FoxP3+ lymphocytes in vulvar melanomas

Abstract

The prognostic role of PDL1 expression, CD8+ and FoxP3+ lymphocytes in vulvar melanomas has not been studied. We correlated PDL1 expression and CD8+ and FoxP3+ immune infiltrates with clinicopathologic variables and patient outcomes in a series of 75 vulvar melanomas. Tumoral PDL1 expression (>5%) was seen in 23% of cases. By Fisher exact test, PDL1 expression and peritumoral FoxP3+ lymphocytes significantly correlated with less disease-specific death. By linear regression analysis, correlations between tumoral PDL1 expression with the density of tumoral CD8+ and peritumoral CD8+ lymphocytes, tumoral FoxP3+ with tumoral CD8+ lymphocytes, and peritumoral FoxP3+ with peritumoral CD8+ lymphocytes were observed. By univariate analyses, tumor thickness >4 mm predicted poorer progression-free survival, melanoma-specific survival, and overall survival. PDL1 expression >5% and peritumoral CD8+, peritumoral FoxP3+, and tumoral FoxP3+ lymphocytes correlated with better overall survival. By multivariate analyses, high peritumoral FoxP3+ lymphocytes independently predicted better melanoma-specific survival (P = .023), and tumor thickness independently predicted poorer progression-free survival (P = .05) and overall survival (P = .039). In conclusion, our study shows that, independent from tumor thickness, an increased density of peritumoral FoxP3+ lymphocytes may positively impact survival in a subset of vulvar melanomas. Tumoral PDL1 expression correlated with tumoral as well as peritumoral CD8+ and FoxP3+ lymphocytes, supportive of an adaptive immune response. Although the frequency of PDL1 expression is low in vulvar melanoma, its expression may identify a subset of vulvar melanoma that might respond to immunotherapy.