CD274 and adenoma: In these examples, PD-L1 staining in epithelial and/or ICs gradually increased following tumor progression: from sessile serrated adenomas with low-grade dysplasia to colonic adenocarcinomas [28], from ductal carcinoma in situ to invasive ductal carcinoma of the breast [27], and finally from normal cervix/LSIL to HSIL, SCC, and metastatic SCC [31].