Taken together, these insights into ASCL1 vs. NEUROD1 expression within NEPC and SYP expression in PRAD argue for a standardized IHC panel-based approach using ASCL1, NEUROD1, INSM1, and SYP, in conjunction with histomorphological assessment, to add greater precision to the diagnosis and treatment of NEPC. Here, INSM1 is linked to prostate adenocarcinoma.