Immune checkpoint status and tumor microenvironment in vulvar squamous cell carcinoma

Vulvar squamous cell carcinoma accounts for 5% of cancers of the female genital tract. Current guidelines recommend wide local excision with negative surgical margins as the standard treatment. However, the extent of the tumor-free resection margin after wide local excision is still controversial in many cases. Drugs targeting immune checkpoints such as PD-1 or its ligand PD-L1 have potential clinical utility in these patients. We examined the expression of PD-L1 in tumor cells and immune cells, as well as the proportion of PD-1, CD8, and FOXP3 positive lymphocytes. Twenty-one cases of invasive vulvar squamous cell carcinomas were reviewed. Whole slides of representative formalin-fixed, paraffin-embedded archival material were used for analysis. Odds ratios (OR) and hazard ratios (HR) were used to estimate risk for disease recurrence, overall mortality, and cancer mortality. PD-L1 expression was found in 43% of tumor cells, with higher proportions in intratumoral (67%) and peritumoral (81%) immune cells. OR and HR for disease recurrence and cancer mortality were higher in tumors with higher CD8 expression. OR and HR for overall mortality were also higher in tumors with higher PD-L1 and CD8 expression. In conclusion, nearly half of cases were PD-L1 positive in tumor cells with over two-third of cases demonstrating PD-L1 positivity in immune cells. Immunohistochemical expression of PD-L1 and CD8 could be used to suggest higher risk of disease recurrence, overall mortality, and cancer mortality. Furthermore, our data contributes to the growing evidence that targeting the PD-1/PD-L1 pathway may be beneficial in vulvar squamous cell carcinomas.