Expression of Programmed Cell Death-L1 (PD-L1) Protein and Mismatch Repair Mutations in Orbital Tumours-a Pilot Study.

Our study demonstrated scattered, non-quantifiable or absent PD-L1 staining in a limited sample of orbital tumours suggesting that PD-1/PD-L1 inhibitor therapy may not be useful in treatment of malignant orbital tumours (rhabdomyosarcoma and ACC) when refractory to conventional therapy. Our pilot study suggest that PD-L1/MMR axis might not play a major role in the pathogenesis of primary orbital tumour.