Pd‐l1 expression in 65 conjunctival melanomas and its association with clinical outcome

Abstract

Conjunctival melanoma (CM) is a rare and aggressive tumour that is increasing in frequency. The prognostic value of PD‐L1 expression, alone or in combination with CD8 and PD‐1 expression and the BRAF and NRAS status, has not been determined in CM to date. We evaluated the expression of PD‐L1, CD8, PD‐1 in CM and investigated whether there was an association between the expression of these markers and the BRAF and NRAS molecular profile as well as some clinico‐pathological criteria. A total of sixty‐five CM were assessed for PD‐L1, PD‐1, and CD8 expression by immunohistochemistry (IHC) and for BRAF and NRAS genomic alterations using molecular biology techniques and anti‐BRAF and anti‐NRAS antibodies. PD‐L1 expression in tumour cells (TC) was very low or absent but detected in tumour‐infiltrating immune cells (IC). A correlation was observed between the expression of PD‐L1, CD8, and PD‐1 in IC. No correlation between PD‐L1 expression (in tumour and/or immune cells) and BRAF or NRAS mutations was observed. PD‐L1 expression in IC correlated with a higher pTNM stage and PD‐L1 expression in TC with worse disease‐specific survival. PD‐L1 expression is a potential prognostic biomarker that correlates with poor prognosis in CM patients.