Similar results were found when all NEC or SCNEC were compared to grade 3 IDC-NST in the large publicly available METABRIC dataset, in which TP53/RB1 co-alteration was reported in only 3% (35/1009) tumors (p < 0.001, p < 0.001, and p = 0.007, respectively) (Supplementary Fig. S3). Here, TP53 is linked to neuroendocrine carcinoma.