Although SOX2 is also expressed in immature teratomas (Phi et al., 2007; Nonaka, 2009; Liang et al., 2015), thymomas (but not normal thymic tissue) (Cimpean et al., 2011), ovarian adenocarcinomas (Ye et al., 2011) and also breast cancer, particularly in early stage breast lesions (Lengerke et al., 2011; Leis et al., 2012), we failed to demonstrate a significant immune response to SOX2 antigens in patients with tumours other than SCLC, whether these tumours were seen in the context of a PND or not. This evidence concerns the gene SOX2 and breast carcinoma.