Concordance of tumor infiltrating lymphocytes, PD-L1 and p16 expression in small biopsies, resection and lymph node metastases of oropharyngeal squamous cell carcinoma.

Abstract

The incidence of oropharyngeal squamous cell carcinoma (OPSCC), especially human papillomavirus (HPV)-associated, is increasing worldwide. Immunotherapy become available for patients with carcinomas in the head and neck region, however without ideal biomarker. Markers like PD-L1 vary in the clone of the antibody used, and the method of evaluation. Adequate and reliable immune cells characterization and evaluation is still not found. Furthermore, studies analyzing representativeness of different tissue samples are scarce. We analyzed small biopsy, lymph node (LN) metastasis and resected OPSCC, in regards of tumor infiltrating lymphocyte (TIL) density, PD-L1 and p16 expression. Patients with OPSCC diagnosed from 2000 to 2016, with small biopsy, resection specimen and LN metastasis samples were selected. We analyzed TILs on hematoxylin-eosin stain, and PD-L1 and p16 expression in tumor cells. Concordance between different tumor locations was evaluated. 93 patients, with 65 small biopsies, 72 resection specimens, and 70 LN metastases were included. TILs, p16 and PD-L1 demonstrated very high concordance. Additionally, PD-L1 expression in the small biopsies was more representative of the PD-L1 expression in the resection specimens, than the LN samples. TILs density can be reliably assessed using hematoxylin-eosin stain with high concordance between the small biopsy, resection specimen and LN metastasis. Evaluation of concordance of p16 expression is very high, nevertheless some cases might be misdiagnosed on a small biopsy or lymph node metastasis. Evaluation of PD-L1 expression is very reliable on the biopsy specimen. Different PD-L1 clones and methods of evaluation still remain to be addressed.