LAUSR

http://dx.doi.org/10.1016/j.oraloncology.2017.06.019 1368-8375/ 2017 Elsevier Ltd. All rights reserved. Dear editor, We are quite interested in the recently published article entitled ‘‘Programmed death ligand 1 (PD-L1) expression and tumor microenvironment: Implications for patients with oral precancerous lesions” [1]. The authors had explored the PD-L1 expression in the stoma cells in oral precancerous lesions and investigated the relationships among PD-L1 positive cells and malignant transformation of these cells. We have two questions on this article. First, In this article, the authors indentified CD163 as the maker of tumor associated macrophages (TAM) which had a phenotype of protumoral function which is similar to M2 macrophages, as indicated in the article. However, we do not quite agree to name these macrophages as TAM. TAM indicates those macrophages in tumor microenvironment especially malignant tumors [2]. As we know, oral precancerous lesions are not tumors, so these macrophages should not be called as TAM. Besides, TAM should originate from bone marrow [2]. However, no existed studies have proved that macrophages in oral precancerous lesions are from the bone marrow. Finally, TAM should have a M2 phenotype, but in Mori et al.’s [3] study, they have found that in oral precancerous lesions, CD163 positive cells may have an M1 phenotype, which challenged the use of CD163 as the marker of ‘‘TAM” in this situation. Second, in Figure 3A of this article, we found that nearly 100% of PD-L1 positive cells were macrophages, however, Figure 3B indicated that some PD-L1 positive cells were CD8 positive lymphocyte which is quite confusing. We would like to know how to explain this. Conflict of interest statement