KRAS and Patent ductus arteriosus: The most recent subcategories proposed for PDA include four subtypes: (1) pancreatic progenitor or classical PDA, which express early pancreatic development genes (i.e., PDX1, FOXA2/3, HES1); (2) squamous or quasimesenchymal tumors, which have increased TP53 mutations, upregulated TP63ΔN and activated TGF-β signaling and MYC pathways and a poor prognosis; (3) aberrantly differentiated endocrine/exocrine tumors, which overexpress genes involved in KRAS activation and exocrine (NR5A, RBPJL) and endocrine (NEUROD1, NKX2-2) markers; and (4) immunogenic PDA.