Signatures associated with DNA mismatch repair (MMR) deficiency (https://cancer.sanger.ac.uk/cosmic/signatures_v2, accessed on 10 May 2020), namely, signatures 6 and 21, were identified in one biliary ITPN (case # 8) harboring a STOP mutation in the tumor suppressor gene BAP1. Of note, none of the cases showed a predominance of signature 3, a signature associated with BRCA1/2 mutations [16]. This evidence concerns the gene BAP1 and hyperinsulinemic hypoglycemia, familial, 4.