ABSTRACT
BACKGROUND: Programmed cell death ligand 1 (PD-L1) plays a major role in the immune responses of a variety of cancers. Recently, several studies revealed that PD-L1 is differently expressed in some cases of non-melanoma skin cancer. The expression of PD-L1 in cutaneous squamous cell carcinoma has not yet been described in Korea. OBJECTIVE: To investigate the expression of PD-L1 in cutaneous squamous cell carcinoma and its association with variable clinicopathological factors. METHODS: We performed immunohistochemical staining of 52 cutaneous cell carcinoma cases, including 28 high-risk cases and 24 low-risk cases. Cases were selected from patients who had visited the department of dermatology of our hospital from 2001 to 2017. The expression patterns were assessed using the H-score. Cases demonstrating at least 1+ of PD-L1 in more than 1% of tumor cells were considered positive. RESULTS: PD-L1 expression of tumor cells was 19.2% (10/52) for all cases, 0.0% (0/24) for the low-risk group, and 35.7% (10/28) for the high-risk group. PD-L1 positive cutaneous squamous cell carcinoma cases showed a significantly higher proportion of large tumors and tumors with deep invasion and a higher lymphatic metastasis rate when compared to PD-L1 negative cutaneous squamous cell carcinoma cases. CONCLUSION: Our study shows that cutaneous squamous cell carcinoma exhibits PD-L1 expression in 19.2% of cases. PD-L1 positive tumors are associated with high-risk cases of cutaneous squamous cell carcinoma, which may help guide the choice of therapeutic strategy.