CD274 and neoplasm: The most accepted classification system of these kinds of carcinomas is the AEG classification system according to Siewert based on the tumor location and was supplemented via the Cancer Genome Atlas (TCGA) by non-clinical features such as Epstein–Barr virus infections, microsatellite instability status or PD-L1 and PD-L2 amplification (Cancer Genome Atlas Research et al. 2014; Siewert and Allgöwer 2001; Cancer Genome Atlas Research et al. 2017).