In contrast to the NEC, none of the other grade 3 cancers showed aberrant RB or p53 expression patterns (RB loss in 83% NEC vs 0% grade 3 NET, p = 0.001; aberrant p53 in 60% NEC vs 0% grade 3 NET, p = 0.013), and none were diffusely p16 positive (82% NEC vs 0% grade 3 NET, p = 0.002). Here, RB1 is linked to neuroendocrine carcinoma.