The immune check point inhibitor PD-L1 was expressed in only 2 (13 %) of 15 type A thymomas, but 13 (76 %) of 17 B3 thymomas and 16 (53 %) of 30 thymic carcinomas (Table 4, Fig. 7, Supplementary Fig. S4). This evidence concerns the gene CD274 and thymoma.