[Comparison of programmed death-ligand 1 protein expression between primary tumors and lymph node metastatic lesions...

Objective: To investigate the difference of programmed death-ligand 1 (PD-L1) expression between primary lesions and lymph node metastatic lesions in oral squamous cell carcinoma. Methods: Eighty-two patients diagnosed with oral squamous cell carcinoma from December 2020 to July 2021 in Department of Oral Pathology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine & College of Stomatology, Shanghai Jiao Tong University, were enrolled in this study. All the patients underwent neck dissection concurrently and had lymph node metastasis. Among them, there were 28 females and 54 males. The age range was 24-79 years old [(58.6±11.7) years old]. The expression of PD-L1 protein in primary tumors and lymph node metastatic lesions was detected by immunohistochemistry. Combined positive score (CPS) was used to evaluate the PD-L1 expression. And the difference of PD-L1 expression between primary tumors and metastatic lesions was analyzed. Results: Among 82 primary tumors, 9 cases (11%) had PD-L1 CPS<1, 31 cases (38%)≥ 1 and <20, and 42 cases (51%)≥20. Cases with perineural invasion had lower CPS (χ²=6.35, P=0.042). Among 82 matched lymph node metastatic lesions, 9 cases (11%) had CPS<1, 38 cases (46%)≥1 and<20, and 35 cases (43%)≥20. The CPS of 27 pairs (33%) of primary and metastatic lesions were discordant. The statistical results showed that the Kappa value of consistency evaluation was 0.446, indicating that the consistency of PD-L1 CPS in primary and metastatic lesions of OSCC was medium. Conclusions: There are differences in PD-L1 expression between the primary lesion of OSCC and cervical lymph node metastatic lesions, and the consistency is medium. In the routine practice, lymph node metastatic lesions should be carefully used to replace the primary lesion for PD-L1 CPS evaluating.