PAX5 and lymphoma: Kiyasu et al. [5] defined PD-L1 positivity in tumor cells as over 30% of lymphoma cells staining of both PD-L1 and paired box gene 5 (PAX5); when PD-L1-positive non-malignant stromal cells constituted over 20% of the total tissue from patients without PD-L1 expression in tumor cells, the sample was considered PD-L1-positive in tumor microenvironment.