Objective To detect the expression of programmed cell death ligand 1 (PD-L1) in papillary thyroid carcinoma (PTC) and PTC with coexistent Hashimoto’s thyroiditis (HT) tissues, and to explore its clinical significance of its expression.Methods The PTC patients who underwent thyroidectomy at the Thyroid Surgery Department of the Affiliated Hospital of Guizhou Medical University from March 2017 to May 2019 were retrospectively collected. Immunohistochemical staining was used to detect the expression of PD-L1 in the PTC tissues, PD-L1 staining positive cells ≥20% was judged as positive expression, <20% was judged as negative expression. The relationship between PD-L1 positive expression rate and clinicopathologic characteristics of patients with PTC were analyzed, and the correlation between the presence of HT in PTC tissues and PD-L1 positive expression was studied.Results A total of 138 patients with PTC were included in this study, including 104 patients with PTC alone and 34 PTC patients with coexistent HT. The positive rate of PD-L1 expression in the 138 cases of PTC tissues was 35.5% (49/138), among which was 43.3% (45/104) in the pure PTC tissues, and 11.8% (4/34) in the PTC tissues with HT, the latter was significantly lower than the former (P=0.001). The results of univariate analysis showed that the positive rate of PD-L1 expression was related to the tumor size, the presence or absence of extraglandular invasion and HT in PTC patients (P<0.05), and the results of Spearman correlation analysis showed that the positive rate of PD-L1 expression was positively correlated with tumor size (r_s=0.173, P=0.041) and extraglandular invasion (r_s=0.197, P=0.021), and negatively correlated with whether TH was merged (r_s=–0.284, P=0.001). The multivariate analysis results showed that the positive rate of PD-L1 expression was closely related to whether PTC with coexistent HT [OR=5.720, 95%CI (1.879, 17.411), P=0.002], and it was not found to be related to tumor size and presence of extraglandular invasion (P>0.05).Conclusions Positive rate of PD-L1 expression has a certain relationship with tumor size and presence or absence of extraglandular invasion, and which in PTC patients with or without HT is significantly different, that is, positive rate of PD-L1 expression in PTC with HT is lower suggests that coexistent HT might be an inhibitory factor in occurrence of PTC, and immune microenvironment-related factors of PTC might be involved in occurrence and development of thyroid cancer.

Citation： LUO Xue, ZHAO Daiwei, CHEN Song, GAO Qingjun. Expression of programmed cell death ligand 1 in papillary thyroid carcinoma with coexistent Hashimoto’s thyroiditis and its clinical significances. CHINESE JOURNAL OF BASES AND CLINICS IN GENERAL SURGERY, 2021, 28(9): 1155-1158. doi: 10.7507/1007-9424.202012040 Copy