Our earlier findings are consistent with the idea that full transformation of PNECs to form malignant SCLC requires additional changes beyond restricted expression of the tumor suppressor genes RB1 and TP53, such as heightened expression of a proto-oncogene in the MYC family (Ireland et al., 2020; Mollaoglu et al., 2017). This evidence concerns the gene TP53 and small cell lung carcinoma.