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IgG4-related sclerosing cholangitis (IgG4-SC) is recognized as a benign steroid-responsive disease; however, little is known about the risk of development of cancer in patients with IgG4-SC and about how to counter this risk.We conducted a retrospective review of the data of 924 patients with IgG4-SC selected from a Japanese nationwide survey. The incidence, type of malignancy, and risk of malignancy in these patients were examined. Then, the standardized incidence ratio (SIR) of cancer in patients with IgG4-SC was calculated.Relapse was recognized in 19.7% (182/924) of patients, and cancer development was noted in 15% (139/924) of patients. Multivariate analysis identified only relapse as an independent risk factor for the development of cancer. In most of these patients with pancreato-biliary cancer, the cancer developed within 8 years after the diagnosis of IgG4-SC. The SIR for cancer after the diagnosis of IgG4-SC was 12.68 (95% confidence interval [CI] 6.89-8.79). The SIRs of cancers involving the biliary system and pancreas were 27.35 and 18.43, respectively. The cumulative survival rate was significantly better in the group that received maintenance steroid treatment (MST) than in the group that did not; thus, MST influenced the prognosis of these patients.Among the cancers, the risk of pancreatic and biliary cancers is the highest in these patients. Because of the elevated cancer risk, surveillance after the diagnosis and management to prevent relapse are important in patients with IgG4-SC to reduce the risk of development of cancer.

We attempted to determine the indications and limitations of steroid therapy as the first-line therapy in patients with autoimmune pancreatitis (AIP) with cyst formation (ACF).This Japanese multicenter survey was conducted to examine the merits/demerits of steroid treatment as the initial therapy for ACF.Data of a total of 115 patients with ACF were analyzed. Complete remission was achieved in 86% (86/100) of patients who had received steroid treatment, but only 33.3% (5/15) of patients who had not received steroids. Relapse after the remission (n = 86) occurred in 7.6% (6/86) of patients who had received steroid therapy, but 40% (2/5) of patients who had not received steroid therapy. Multivariate analysis identified adoption of the wait and watch approach without steroid treatment (odds ratio = 0.126, P .001) as a significant and independent negative predictor of remission of ACF. As for predictors of relapse, the presence of varix (odds ratio = 5.83, P = .036) was identified as an independent risk factor.Steroid therapy plays an important role as first-line therapy in AIP patients with pancreatic cyst formation, however, varix formation, besides the diameter of the cyst(s), is a risk factor for refractoriness to steroid therapy.

Although long-term stent placement using endoscopic gallbladder stenting (EGBS) reportedly reduces cholecystitis recurrence in patients unfit to undergo cholecystectomy, its efficacy and safety remain uncertain.This study aimed to examine the long-term effect of EGBS in poor surgical candidates of cholecystectomy.A total of 528 high-risk surgical patients with acute calculous cholecystitis met this study's eligibility criteria. The technical success and adverse events (AE) were compared between patients who underwent EGBS and those who underwent percutaneous transhepatic gallbladder drainage (PTGBD). Elective stent exchange and removal were not performed after EGBS. The external tube was removed after improvement of cholecystitis following PTGBD.The technical success rate was significantly lower with EGBS compared to PTGBD (75.4% versus 98.7%, P 0.001), while the early-AE rate did not differ significantly between the two methods (7.7% versus 4.3%, P = 0.146). The 1-, 3-, and 5-year cumulative incidence rates of cholecystitis were 3.8%, 7.2%, and 7.2% with EGBS, and 11.7%, 17.6%, and 30.2% with PTGBD, respectively (P = 0.001). Conversely, those of symptomatic late-AE (except cholecystitis) were 8.2%, 22.7%, and 31.4% with EGBS, and 7.5%, 10.9%, and 13.1% with PTGBD, respectively (P = 0.035). Thus, the 1-, 3-, and 5-year cumulative incidence of overall late-AE was 12.0%, 30.4%, and 40.4% with EGBS, and 19.2%, 28.3%, and 42.5% with PTGBD, respectively (P = 0.649).Long-term stent placement via EGBS is useful for preventing the recurrence of cholecystitis, but the success rate is low and the frequency of other late-AE increases with the prolongation of the indwelling period.

Supplementary Figure S1: Cell viability in pancreatic cancer cells treated by talaporfin with or without irradiation. Supplementary Figure S2: The luciferase luminescence intensities in AsPC1/luc cells treated by PDT with talaporfin or Mal3-chlorin. Cells were treated with talaporfin (1-16 μM) or Mal3-chlorin (0.1-2 μM) at 37{degree sign}C for 4 h, and then irradiated. After incubation for 24 h, cells were incubated for a short time at 37{degree sign}C with D-luciferin (150 μg/mL, Wako, Ltd.) in media. Luminescence was measured using a Lu mat LB 9507 instrument (EG&G BERTHOLD) and the data were normalized against the average value of non-treated cells. Values are means {plus minus} SD, n = 4 in each. Supplementary Figure S3: Average body weight transitions of mice during the experiment. Values are means {plus minus} SD, n = 7 in each. Supplementary Figure S4: Images of representative abdominal skin of mice from each group. Representative imaging of abdominal skin from mice at day 1, 8, and 15 on the treatment regimen as shown in Figure 4A: Control mice (left panel), talaporfin-mediated PDT mice (middle panel), and Mal3-chlorin-mediated PDT mice (right panel). Supplementary Figure S5: Involvement of GLUT1 in the uptake of Mal3-chlorin into pancreatic cancer cells. AsPC1/luc or BxPC3/luc cells were seeded into 96-well culture plates at a concentration of 5 Ã- 103 cells/well and incubated overnight. Cells were subsequently treated with WZB117 (0.1-30 μM; EMD Chemicals, San Diego, CA, USA), which is a pharmacological GLUT1 inhibitor. After incubation for 24 h, cells were incubated for 4 h with Mal3-chlorin (1 μM) and WZB117 (0.1-30 μM), and levels of specific fluorescence were measured by Spectrafluor Plus (excitation; 405 nm, emission; 660 nm). The data were normalized against the average value of non-treated cells. Values are means {plus minus} SD, n = 6 in each. Supplementary Figure S6: Correlation between the fluorescence intensities and the dose of Mal3-chlorin or the number of cells. AsPC1/luc cells were seeded into 96-well culture plates at a concentration of 1 Ã- 103 - 8 Ã- 103 cells/well and incubated overnight. Cells were subsequently incubated for 4 h with Mal3-chlorin (0.05-2 μM) and then fluorescence levels were measured using a Spectrafluor Plus (excitation; 405 nm, emission; 660 nm). Values are means {plus minus} SD, n = 6 in each.

Images of representative abdominal skin of mice from each group.

The effects of PDT with Mal3-chlorin on ascites formation

Background The frequency of metastasis to the pancreas is very low, and the frequency of metastasis from squamous cell carcinoma of the esophagus is even lower. Although curative resection of these metastatic lesions has been reported for some patients, the survival benefit of these procedures has not yet been clearly determined. Case presentation The patient was a 54-year-old man who was found to have lower thoracic esophageal cancer. Computed tomography showed a 2-cm tumor in the tail of his pancreas. Since no other obvious distal metastases were observed, the patient underwent simultaneous surgical procedures that excised both the esophageal squamous cell carcinoma and the pancreatic metastasis. Histopathologic examination confirmed squamous cell carcinoma in both specimens. The patient has been free of disease for 9 months since the resection. A literature review of all relevant cases to date found that the site of the primaries of all cases of esophageal cancers with metastasis to the pancreas was the lower thoracic esophagus. Conclusion Complete simultaneous resections of esophageal squamous cell carcinoma and a solitary metastasis to the pancreas is beneficial and may produce good outcomes. However, because of the low number of such reports, further studies are needed to confirm the benefits of surgery.

Nab -paclitaxel and gemcitabine (GnP) or FOLFIRINOX (a combination of leucovorin, fluorouracil, irinotecan, and oxaliplatin [FFX]) is currently recognized as the standard first-line regimen for unresectable pancreatic ductal adenocarcinoma (PDAC). Class III β-tubulin (TUBB3) has the potential to predict resistance to taxane in various tumors; therefore, this study aimed to clarify whether TUBB3 is a predictive marker for GnP response.We retrospectively reviewed 113 patients with PDAC who received GnP or FFX as first-line chemotherapy and examined immunohistochemically the TUBB3 expression in specimens obtained by endoscopic ultrasound-guided fine-needle aspiration.High TUBB3 expression was associated with a significantly lower disease control rate ( P = 0.017) and shorter progression-free survival (PFS) ( P = 0.019), and multivariate analysis revealed that TUBB3 expression was an independent variable for PFS in the GnP first-line group ( P = 0.045). In addition, in the FFX first-line group, TUBB3 expression was not correlated with PFS or overall survival (OS). In all 113 patients, TUBB3 expression was not also associated with OS.Class III β-tubulin might be a predictive factor for the response of GnP, but not a prognostic factor for OS, helping the selection of an optimized first-line chemotherapy regimen for unresectable PDAC.

The histological diagnosis of type 1 autoimmune pancreatitis (AIP) based on the findings obtained by an endoscopic ultrasound-guided fine needle biopsy (EUS-FNB) is feasible, but the diagnostic consistency of this method has not been confirmed. We determined the interobserver agreement among 20 pathologists regarding the diagnosis of type 1 AIP, including the distinction from pancreatic ductal adenocarcinoma (PDAC) using large tissue samples obtained by EUS-FNB. After guidance for diagnosing AIP with biopsy tissues was provided, a round 2 was performed. The median sensitivity and specificity for diagnosing PDAC vs. non-neoplastic diseases were 95.2% and 100%, respectively. In groups of specialists (n = 7) and the generalists (n = 13), Fleiss’ к-values increased from 0.886 to 0.958 and from 0.750 to 0.816 in round 2. The concordance was fair or moderate for obliterative phlebitis and storiform fibrosis but slight for ductal lesion of type 1 AIP. Discordant results were due to ambiguous findings and biopsy tissue limitations. Among the specialists, the ratio of cases with perfect agreement regarding the presence of storiform fibrosis increased in round 2, but agreement regarding obliterative phlebitis or ductal lesions was not improved. Although the histological definite diagnosis of type 1 AIP was achieved by most observers in > 60% of the cases, the confidence levels varied. Because some ambiguities exist, the histological diagnostic levels based on the diagnostic criteria of type 1 AIP should not be taken for granted. Guidance is effective for improving accurate PDAC diagnoses (notably by recognizing acinar-ductal metaplasia) and for evaluating storiform fibrosis.

Background The clinical characteristics of IgG4-related sclerosing cholangitis (IgG4-SC) especially without autoimmune pancreatitis (AIP) have not been investigated in a large cohort. Aims To clarify the clinical characteristics of IgG4-SC and IgG4-SC without AIP. Methods We retrospectively reviewed imaging, serology, other organ involvement (OOI) and histology of 872 patients with IgG4-SC who participated in a Japanese nationwide survey in 2019, and compared these items between IgG4-SC with and without AIP. Results AIP was present in 83.7% (730/872) of IgG4-SC. In IgG4-SC, bile duct wall thickening was observed on ultrasound (528/650; 81.2%), computed tomography (375/525; 71.4%) and magnetic resonance imaging or cholangiopancreatography (290/440; 65.9%). An elevated serum IgG4 level (≥ 135 mg/dL) was found in 88.0% (322/366). IgG4-related OOI other than AIP was observed in 25.2% (211/836). The proportion of females was significantly higher in IgG4-SC without AIP (28.9% vs. 20.1%; p = 0.025). Hilar stricture was the most common cholangiographic type in IgG4-SC without AIP (39/107; 36.4%).There were no significant differences between IgG4-SC with and without AIP in the rates of bile duct wall thickening, elevated serum IgG4 level, or IgG4-related OOI. Conclusions The clinical characteristics of IgG4-SC was similar between IgG4-SC with and without AIP in a large cohort.

Sampling of bile juice during endoscopic retrograde cholangiopancreatography (ERCP) has potential benefit of being amenable to the identification of novel biomarkers in liquid biopsy. This study reports the results of a global investigation of exosomal microRNAs (miRNAs) in bile to identify potential biomarkers for biliary tract cancers (BTCs). Eighty-eight bile samples collected during ERCP (45 BTC and 43 noncancer control samples) were enrolled in this study. Eleven BTC samples and nine control samples were assigned as the discovery set. Exosomes in bile and serum samples were collected using a glass membrane column with size-controlled macroporous glass (MPG), and exosomal miRNA expression profiles were evaluated using comprehensive miRNA microarray analysis (3D-Gene). For validation, exosomal miRNA in the bile samples of 34 BTCs and 34 controls were comprehensively evaluated using 3D-Gene. In the discovery set, eight exosomal miRNAs in bile were identified as significant aberrant expression markers, while no miRNA with aberrant expression in serum was identified. In a comparison of the discovery and validation sets, miR-451a and miR-3619-3p were identified as reproducible upregulated markers, and the combination of the two bile miRNAs showed an excellent area under the curve (0.819) value for diagnosing BTCs. In addition, high miR-3619-3p expression in bile reflects poorer prognosis of BTCs (hazard ratio = 2.89). The MPG-extracted exosomal miRNAs in bile aspirated during ERCP provide a convenient new approach for diagnosing biliary diseases. Bile-derived miRNA analysis with miR-451a and miR-3619-3p represents a potentially valuable diagnostic strategy for identifying BTCs as well as a predictive indicator of BTC prognosis.

Background Chronic pancreatitis is a known risk factor of pancreatic cancer (PDAC). A similar association has been suggested but not demonstrated for autoimmune pancreatitis (AIP). Objective The aim of our study was to identify and analyse all published cases of AIP and PDAC co-occurrence, focusing on the interval between the diagnoses and the cancer site within the pancreas. Methods Relevant studies were identified through automatic searches of the MEDLINE, EMBASE, Scopus, and Web of Science databases, and supplemented by manual checks of reference lists in all retrieved articles. Missing/unpublished data were obtained from the authors of relevant publications in the form of pre-prepared questionnaires. Results A total of 45 cases of PDAC in AIP patients were identified, of which 12 were excluded from the analysis due to suspicions of duplicity or lack of sufficient data. Thirty-one patients (94%) had type 1 AIP. Synchronous occurrence of PDAC and AIP was reported in 11 patients (33%), metachronous in 22 patients (67%). In the metachronous group, the median period between diagnoses was 66.5 months (2–186) and a majority of cancers (86%) occurred more than two years after AIP diagnosis. In most patients (70%), the cancer originated in the part of the pancreas affected by AIP. Conclusions In the literature, there are reports on numerous cases of PDAC in AIP patients. PDAC is more frequent in AIP type 1 patients, typically metachronous in character, and generally found in the part of the pancreas affected by AIP.

Biliary strictures caused by inflammation or fibrosis lead to jaundice and cholangitis which often make it difficult to distinguish malignant strictures. In cases when malignancy cannot be excluded, surgery is often performed. The concept of immunoglobulin G4 (IgG4)-related sclerosing cholangitis (SC) as a benign biliary stricture was recently proposed. The high prevalence of the disease in Asian countries has resulted in multiple diagnostic and treatment guidelines; however, there is need to formulate a standardized diagnostic strategy among various countries considering the utility, invasiveness, and cost-effectiveness. We evaluated accuracies of various diagnostic modalities for biliary strictures comparing pathology in the Delphi meetings which were held in Rochester, MN. The diagnostic utility for each modality was graded according to the experts, including gastroenterologists, endoscopists, radiologists, and pathologists from the United States and Japan. Diagnostic utility of 10 modalities, including serum IgG4 level, noninvasive imaging, endoscopic ultrasound, endoscopic retrograde cholangiopancreatography-related diagnostic procedures were advocated and the reasons were specified. Serum IgG4 level, noninvasive imaging, diagnostic endoscopic ultrasound and intraductal ultrasonography under endoscopic retrograde cholangiopancreatography were recognized as useful modalities for the diagnosis. The information in this article will aid in the diagnosis of biliary strictures particularly for distinguishing IgG4-SC from cholangiocarcinoma and/or primary SC.

Histological evidence is essential for diagnosing malignant biliary strictures. However, conventional brush cytology remains the primary method used worldwide, despite its low diagnostic sensitivity and accuracy, as it is technically easy, rapid, and cost-effective. The aim of this study was to evaluate the diagnostic performance of a recently introduced endoscopic scraper, the simplicity of which is comparable to that of a conventional brush, by comparing diagnostic yields and the number of collected cells. The sensitivity of the endoscopic scraper when using the cell block technique was significantly higher than when using brush cytology or a brush with the cell block technique (53.6% vs. 30.9%, p < 0.001; 53.6% vs. 31.6%, p = 0.024, respectively). Quantitative digital image analysis of cell block sections revealed that the median number of cells obtained with the endoscopic scraper was significantly higher than when using the brush (1917 vs. 1014 cells, p = 0.042). Furthermore, seven cases (8.3%; 7/84) were diagnosed by immunohistochemical analysis of the cell block section obtained from the endoscopic scraper. Given its simplicity and greater capacity for sample acquisition, use of the endoscopic scraper in conjunction with the cell block technique could replace brush cytology for the histological diagnosis of malignant biliary strictures.

We herein report a 64-year-old man with concomitant pancreatic ductal adenocarcinoma (PDAC) and type 1 autoimmune pancreatitis (AIP). An endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) from the pancreatic head mass revealed level 2 histology of AIP and atypical glands. We diagnosed definitive focal AIP using the clinical diagnostic criteria. Computed tomography revealed that the pancreatic mass had not been reduced by steroid therapy. Surgery was performed after a histological PDAC diagnosis was made via a transpapillary biliary biopsy. The resected specimen revealed PDAC associated with AIP. It is important to consider the cooccurrence of PDAC and AIP even if the histological diagnosis via an EUS-FNB is AIP.

Background/Aims: Although endoscopic transpapillary gallbladder drainage (ETGBD) has been reported as an alternative procedure for acute cholecystitis, it requires advanced endoscopic techniques. In terms of the certainty of achieving drainage, it remains a challenging procedure. The aim of the current study was to elucidate the practical efficacy of cholangioscopic assistance and to develop a new classification that could be used to evaluate the technical difficulty of ETGBD and provide a theoretical strategy to apply cholangioscopy appropriately for difficult ETGBD. Methods: A total of 101 patients undergoing ETGBD were retrospectively studied. The characteristics and technical outcomes of ETGBD with conventional ETGBD (C-ETGBD) and Spy- Glass DS-assisted ETGBD (SG-ETGBD) were evaluated. The characteristics and technique-dependent factors of unsuccessful C-ETGBD/SG-ETGBD were evaluated using the classification based on the steps of the procedure. The predictive factors of successful C-ETGBD/SG-ETGBD were examined. Results: C-ETGBD was successful in 73 patients (72.3%). SG-ETGBD was successful in 11 of 13 patients (84.6%) who had C-ETGBD failure. Optional SG-ETGBD significantly increased the final success rate (94.1%) compared to C-ETGBD alone (p=0.003). ETGBD procedures could be classified into four steps. SG-assistance worked as an excellent troubleshooter in step 1 (failure to identify the cystic duct orifice) and step 2 (failure of guidewire advancement across the downturned angle of cystic duct takeoff). Magnetic resonance cholangiopancreatography could provide predictive information based on the classification. Conclusions: Optional SG-ETGBD achieved a significantly higher success rate than C-ETGBD alone. Step classification is helpful for determining the technical difficulty of ETGBD and developing a theoretical strategy to apply cholangioscopy in a coordinated manner. (Gut Liver 2021;15:476-485)

An 84-year-old man was admitted with epigastralgia. Computed tomography showed contrast-enhanced wall thickness in the cystic duct. An endoscopic examination revealed short irregular stricture in the cystic duct, and per-oral cholangioscopy revealed a reddish papillary tumor at the stricture site. Surgical resection revealed high-grade biliary intraepithelial neoplasia (BilIN) at the stricture site of the cystic duct. To our knowledge, this is the first case of a solitary high-grade BilIN epithelium in the cystic duct detected by per-oral cholangioscopy.

Peritoneal dissemination and malignant ascites in pancreatic ductal adenocarcinoma (PDAC) patients represent a major clinical issue. Lysophosphatidic acid (LPA) is a lipid mediator that modulates the progression of various cancers. Based on the increasing evidence showing that LPA is abundant in malignant ascites, we focused on autotaxin (ATX), which is a secreted enzyme that is important for the production of LPA. This study aimed to elucidate the importance of the ATX‐LPA axis in malignant ascites in PDAC and to determine whether ATX works as a molecular target for treating peritoneal dissemination. In a PDAC peritoneal dissemination mouse model, the amount of ATX was significantly higher in ascites than in serum. An in vitro study using two PDAC cell lines, AsPC‐1 and PANC‐1, showed that ATX‐LPA signaling promoted cancer cell migration via the activation of the downstream signaling, and this increased cell migration was suppressed by an ATX inhibitor, PF‐8380. An in vivo study showed that PF‐8380 suppressed peritoneal dissemination and decreased malignant ascites, and these results were validated by the biological analysis as well as the in vitro study. Moreover, there was a positive correlation between the amount of ATX in ascites and the degree of disseminated cancer progression. These findings demonstrated that ATX in ascites works as a promotor of peritoneal dissemination, and the targeting of ATX must represent a useful and novel therapy for peritoneal dissemination of PDAC., We could detect the strong inhibitory effect of PF‐8380 on intraperitoneal dissemination of pancreatic ductal adenocarcinoma (PDAC) as it was clearly visualized by bioluminescence imaging and under white‐light imaging.

Endoscopic biliary drainage strategies for managing unresectable malignant hilar biliary obstruction differ in terms of stent type, drainage area, and deployment method. However, the optimal endoscopic drainage strategy remains unclear. Uncovered self-expandable metal stents (SEMS) are the preferred type because of their higher functional success rate, longer time to recurrent biliary obstruction (RBO), and fewer cases of reintervention than plastic stents (PS). Other PS subtypes and covered SEMS, which feature a longer time to RBO than PS, can be removed during reintervention for RBO. Bilateral SEMS placement is associated with a longer time to RBO and a longer survival time than unilateral SEMS placement. Unilateral drainage is acceptable if a drainage volume of greater than 50% of the total liver volume can be achieved. In terms of deployment method, no differences were observed in clinical outcomes between side-by-side (SBS) and stent-in-stent deployment. Simultaneous SBS boasts a shorter procedure time and higher technical success rate than sequential SBS. This review of previous studies aimed to clarify the optimal endoscopic biliary drainage strategy for unresectable malignant hilar biliary obstruction.

The acceptable duration of steroid therapy for patients with IgG4-sclerosing cholangitis (SC) has been under debate. Our aim is to clarify the feasible duration of steroid treatment.We retrospectively reviewed the data of patients with IgG4-SC and analyzed the following: biliary status during the steroid therapy, incidence of remission, relapse, relapse-free survival rate, and steroid-related complications (SRCs).Remission was achieved 99.5% (763/767) of patients who received steroid therapy, while remission rate dropped to 63.6% (78/129) of patients who didn't receive it. Relapse was noted in 19.7% (151/763) of the patients who received steroid. Besides, relapse rate went up 38.4% (30/78) of the counterpart. Normalization of the serum total bilirubin and serum alkaline phosphatase (ALP) levels were achieved at two weeks regardless of biliary drainage. Multivariate analysis identified younger onset, MST less than three years, immunosuppressant, and steroid cessation as independent risk factors for relapse. Steroid-free was achieved in the patients underwent MST only 3.4% over 54 months. SRCs were recorded in a total of 99 patients (12.9%) despite sufficient preemptive medications. Multivariate analysis identified history of malignancy and immunosuppressant as independent risk factors for SRCs.Steroid therapy should be continued for no less than three years to reduce the risk of relapse, with use of preemptive measures taken around five years. The biliary drainage might not be mandatory. Steroid as 1

Background/purpose Epidemiological data on immunoglobulin G4-related sclerosing cholangitis (IgG4-SC) are scarce. Method We randomly selected healthcare facilities from a list of all facilities in Japan. The selection rate was determined according to a stratification based on the facility characteristics and scale. We sent questionnaires to the selected facilities enquiring about the number and sex of patients with IgG4-SC in 2018. Among responding facilities, we further inquired about the clinical characteristics of the patients with IgG4-SC. Results We selected 1,180 departments from health centers across Japan. Of them, 532 (45.1%) responded to the questionnaires. The number of reported patients with IgG4-SC was 1,045, and the estimated point prevalence was 2.18 (95% confidence interval, 2.13-2.23) per 100,000 population. In addition, we enrolled 1,096 patients with IgG4-SC, combining data from previously and newly registered patients. Male patients comprised 79.5% of the population and patients aged 60-80 years had the highest risk for developing the disease. The follow-up period was 5.1±4.0 years and the 5- and 10-year overall survival rates were 95.3% and 89.0%, respectively. Conclusions The point prevalence of IgG4-SC was 2.18 per 100,000 population. The epidemiological features were similar to those observed in previous studies.

The biopsy-based diagnosis of autoimmune pancreatitis (AIP) is difficult but is becoming imperative for pathologists due to the increased amount of endoscopic ultrasound-guided biopsy tissue. To cope with this challenge, we propose guidance for the biopsy diagnosis of type 1 AIP. This guidance is for pathologists and comprises three main parts. The first part includes basic issues on tissue acquisition, staining, and final diagnosis, and is intended for gastroenterologists as well. The second part is a practical guide for diagnosing type 1 AIP based on the AIP clinical diagnostic criteria 2018. Inconsistent histological findings, tips for evaluating IgG4 immunostaining and key histological features including the ductal lesion and others are explained. Storiform fibrosis and obliterative phlebitis are diagnostic hallmarks but are sometimes equivocal. Storiform fibrosis is defined as spindle-shaped cells, inflammatory cells and fine collagen fibers forming a flowing arrangement. Obliterative phlebitis is defined as fibrous venous obliteration with inflammatory cells. Examples of each are provided. The third part describes the differentiation of AIP from pancreatic ductal adenocarcinoma (PDAC), focusing on histological features of acinar-ductal metaplasia in AIP, which is an important mimicker of PDAC. This guidance will help standardize pathology reports of pancreatic biopsies for diagnosing type 1 AIP.