Intrahepatic cholangiocarcinomas were classified into two types based on their microscopic appearance. Tumors with histologic similarities to hilar cholangiocarcinomas (predominantly ductal adenocarcinomas with minor tubular components, if present, restricted to the invasive front) were defined as the perihilar type, whereas the others were classified as peripheral cholangiocarcinomas. Among the 47 cases examined in the present study, 26 (55%) were classified as the perihilar type, whereas 21 (45%) were the peripheral type. The perihilar type had higher pT stages and more frequently showed a periductal-infiltrating gross appearance and microscopic perineural infiltration than peripheral cholangiocarcinomas. The presence of low-grade biliary intraepithelial neoplasia in the adjacent bile ducts was only found in perihilar cholangiocarcinomas (6/21, 29%). The immunophenotype also differed between the two types with MUC5AC and MUC6 being more commonly expressed in the perihilar type. One-third of perihilar cholangiocarcinomas lacked the expression of SMAD4, suggesting SMAD4 mutations, whereas the loss of BAP1 expression and IDH1 mutations were almost restricted to the peripheral type (35 and 15%, respectively). Patients with perihilar cholangiocarcinoma had worse overall survival than those with peripheral cancer (P=0.027). A multivariate analysis identified the histologic classification as an independent prognostic factor (P=0.005, HR=3.638). Comparisons between intrahepatic and hilar cholangiocarcinomas also revealed that the molecular features and prognosis of perihilar cholangiocarcinomas were very similar to those of hilar cholangiocarcinomas. In conclusion, this histology-based classification scheme of intrahepatic cholangiocarcinomas will be useful and clinically relevant because it represents different underlying molecular features and has an independent prognostic value.

Although intracholecystic papillary neoplasms (ICPNs) have been increasingly recognized, their features remain unclear because of the lack of standardized definition. This study aimed to elucidate clinicopathologic and genetic features of ICPNs using stringent diagnostic criteria. On the basis of the recently proposed criteria, gallbladder neoplasms showing delicate papillary growth were diagnosed as ICPNs, while polypoid papillary adenocarcinomas arranged in a complex architecture were categorized as papillary gallbladder cancers (GBCs). Clinicopathologic features were compared among ICPNs (n=7), papillary GBCs (n=24), and nonpapillary GBCs (n=44). Whole-exome and validation Sanger sequencing was also conducted. Gross mucin hypersecretion was detected in 3/7 ICPNs (43%), 1/24 papillary GBCs (4%), and 1/44 nonpapillary GBCs (2%) (P<0.001). All patients with ICPN lacked lymphovascular invasion and nodal metastasis, while these features were occasionally observed in patients with papillary or nonpapillary GBC (13% to 59%). ICPNs were less advanced than papillary and nonpapillary GBCs (P<0.001) with all cases of ICPNs being recurrence-free. Whole-exome and Sanger sequencing identified somatic mutations in STK11 (a causative gene of Peutz-Jegher syndrome; n=3), CTNNB1 (n=2), and APC (a gene of familial adenomatous polyposis; n=1) in ICPNs, while those alterations were exceptional in papillary and nonpapillary GBCs. ICPNs more commonly showed cytoplasmic and/or nuclear expressions of β-catenin than papillary and nonpapillary GBCs. In conclusion, the histology-based classification of gallbladder papillary neoplasms is useful for identifying ICPNs that share clinicopathologic features with the pancreatic counterpart. ICPNs meeting the criteria were genetically distinct from papillary and nonpapillary GBCs, with STK11, CTNNB1, and APC being identified as major driver genes for ICPNs.

Isolated high-grade PanIN may present with pancreatic duct stenosis. Therefore, intensive investigations including pancreatic juice cytology will be required for patients with unexplained pancreatic duct stenosis. The abnormal expression of p53 and SMAD4 is infrequent, while GNAS may be mutated in premalignant lesions mainly affecting the main pancreatic duct, similar to KRAS.

Type 2 autoimmune pancreatitis (type 2 AIP) develops in isolation or sometimes in association with ulcerative colitis. Its diagnosis requires the histologic confirmation of granulocytic epithelial lesions (GELs) with no diagnostic biomarker currently available. This study aimed to elucidate the tissue expression of cytokines and their diagnostic value in this condition. In quantitative polymerase chain reaction for multiple cytokines using tissue-derived mRNA, the expression level of interleukin (IL)-8 was markedly higher in type 2 AIP than in type 1 AIP (P<0.001). In immunostaining, IL-8 expression was detected in the ductal/ductular epithelium (11/13; 85%) and infiltrating neutrophils or lymphocytes (12/12; 100%) in type 2 AIP, but was almost entirely negative in type 1 AIP (n=13; both, P<0.001). Although obstructive pancreatitis adjacent to pancreatic cancers (peritumoral pancreatitis) exhibited IL-8 expression in the epithelium (3/12; 25%) and inflammatory cells (10/12; 83%), expression levels were significantly lower than those in type 2 AIP (P<0.001 and 0.020, respectively). The presence of either GELs or IL-8-positive epithelium discriminated type 2 AIP from type 1 AIP or obstructive pancreatitis with 92% sensitivity and 92% to 100% specificity. Furthermore, CD3/IL-8-coexpressing lymphocytes were almost restricted to type 2 AIP. Interestingly, a similar pattern of IL-8 expression was also observed in colonic biopsies of ulcerative colitis. In conclusion, the overexpression of IL-8 may underlie the development of GELs in type 2 AIP, and IL-8 immunostaining or IL-8/CD3 double staining may become an ancillary method for its diagnosis. The similar expression pattern of IL-8 in ulcerative colitis also suggests a pathogenetic link between the 2 conditions.

Large-duct type iCCA shared the molecular features with pCCA, and it may be reasonable to expand the definition of pCCA to include cancers originating from the second bile duct branches.