Programmed Death-Ligand 1 and Programmed Death-Ligand 2 Expression Can Affect Prognosis in Extramammary Paget’s Disease

Background Extramammary Paget's disease (EMPD) is a type of carcinoma that usually progresses slowly but may cause metastasis and subsequent death of patients. We investigated the relationship between the expression of programmed death-ligand 1 (PD-L1)/programmed death-ligand 2 (PD-L2) and stromal CD8+ tumor-infiltrating lymphocytes (TILs) in EMPD and clinicopathological findings, including prognosis. Materials and methods We examined 47 cases of EMPD and performed immunohistochemical staining of formalin-fixed paraffin-embedded full-face sections. Results PD-L1 expression in tumor cells was observed in 13 cases (27.7%) while PD-L2 expression was observed in 21 cases (44.7%). The cumulative postoperative recurrence-free rate in the group with positivity for PD-L1 and/or PD-L2 with a low CD8+ TIL count was significantly lower than that of the corresponding group with a high CD8+ TIL count and of the PD-L1- and PD-L2-negative group (p=0.026). Conclusion The expression of PD-L1/PD-L2 in tumor cells was shown to be a factor for poor prognosis.