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We construct a new relativistic viscous hydrodynamics code optimized in the Milne coordinates. We split the conservation equations into an ideal part and a viscous part, using the Strang spitting method. In the code a Riemann solver based on the two-shock approximation is utilized for the ideal part and the Piecewise Exact Solution (PES) method is applied for the viscous part. We check the validity of our numerical calculations by comparing analytical solutions, the viscous Bjorken’s flow and the Israel–Stewart theory in Gubser flow regime. Using the code, we discuss possible development of the Kelvin–Helmholtz instability in high-energy heavy-ion collisions.

During the coronavirus disease 2019 pandemic, whether endoscopy generates aerosols needs to be determined. In patients undergoing upper gastrointestinal endoscopy with an enclosure covering their heads, 0.3-10-μm aerosols were measured for 60 seconds before, during, and after endoscopy by an optical counter. Whether aerosols increased in the situation with and without endoscopy was examined. The analysis included 103 consecutive patients undergoing endoscopy and 90 control patients. Aerosols increased significantly during endoscopy compared with the control group. Body mass index and burping were significant factors related to increased aerosols during endoscopy. Upper gastrointestinal endoscopy was an aerosol-generating procedure.

BackgroundGastric adenocarcinoma of fundic-gland type (GA-FG) is a rare variant of gastric neoplasia. However, the etiology, classification, and clinicopathological features of gastric epithelial neoplasm of fundic-gland mucosa lineage (GEN-FGML; generic term of GA-FG related neoplasm) are not fully elucidated. We performed a large, multicenter, retrospective study to establish a new classification and clarify the clinicopathological features of GEN-FGML.MethodsOne hundred GEN-FGML lesions in 94 patients were collected from 35 institutions between 2008 and 2019. We designed a new histopathological classification of GEN-FGML using immunohistochemical analysis and analyzed via clinicopathological, immunohistochemical, and genetic evaluation.ResultsGEN-FGML was classified into 3 major types; oxyntic gland adenoma (OGA), GA-FG, and gastric adenocarcinoma of fundic-gland mucosa type (GA-FGM). In addition, GA-FGM was classified into 3 subtypes; Type 1 (organized with exposure type), Type 2 (disorganized with exposure type), and Type 3 (disorganized with non-exposure type). OGA and GA-FG demonstrated low-grade epithelial neoplasm, and GA-FGM should be categorized as an aggressive variant of GEN-FGML that demonstrated high-grade epithelial neoplasm (Type 2 > 1, 3). The frequent presence of GNAS mutation was a characteristic genetic feature of GEN-FGML (7/34, 20.6%; OGA 1/3, 33.3%; GA-FG 3/24, 12.5%; GA-FGM 3/7, 42.9%) in mutation analysis using next-generation sequencing.ConclusionsWe have established a new histopathological classification of GEN-FGML and propose a new lineage of gastric epithelial neoplasm that harbors recurrent GNAS mutation. This classification will be useful to estimate the malignant potential of GEN-FGML and establish an appropriate standard therapeutic approach.

Advanced colorectal cancer harbors extensive intratumor heterogeneity shaped by neutral evolution; however, intratumor heterogeneity in colorectal precancerous lesions has been poorly studied. We perform multiregion whole-exome sequencing on ten early colorectal tumors, which contained adenoma and carcinoma in situ. By comparing with sequencing data from advanced colorectal tumors, we show that the early tumors accumulate a higher proportion of subclonal driver mutations than the advanced tumors, which is highlighted by subclonal mutations in KRAS and APC . We also demonstrate that variant allele frequencies of subclonal mutations tend to be higher in early tumors, suggesting that the subclonal mutations are subject to selective sweep in early tumorigenesis while neutral evolution is dominant in advanced ones. This study establishes that the evolutionary principle underlying intratumor heterogeneity shifts from Darwinian to neutral evolution during colorectal tumor progression. Advanced colorectal cancers are characterised by intra-tumour heterogeneity dictated by neutral evolution. Here the authors analyse early colorectal tumours by whole-exome sequencing and find that Darwinian evolution determines the fate of early lesions in colorectal adenoma and carcinoma in situ.

BackgroundPancreatic neuroendocrine neoplasms (PanNENs) are a heterogeneous group of tumors. Although the prognosis of resected PanNENs is generally considered to be good, a relatively high recurrence rate has been reported. Given the scarcity of large-scale reports about PanNEN recurrence due to their rarity, we aimed to identify the predictors for recurrence in patients with resected PanNENs to improve prognosis.MethodsWe established a multicenter database of 573 patients with PanNENs, who underwent resection between January 1987 and July 2020 at 22 Japanese centers, mainly in the Kyushu region. We evaluated the clinical characteristics of 371 patients with localized non-functioning pancreatic neuroendocrine tumors (G1/G2). We also constructed a machine learning-based prediction model to analyze the important features to determine recurrence.ResultsFifty-two patients experienced recurrence (14.0%) during the follow-up period, with the median time of recurrence being 33.7 months. The random survival forest (RSF) model showed better predictive performance than the Cox proportional hazards regression model in terms of the Harrell’s C-index (0.841 vs. 0.820). The Ki-67 index, residual tumor, WHO grade, tumor size, and lymph node metastasis were the top five predictors in the RSF model; tumor size above 20 mm was the watershed with increased recurrence probability, whereas the 5-year disease-free survival rate decreased linearly as the Ki-67 index increased.ConclusionsOur study revealed the characteristics of resected PanNENs in real-world clinical practice. Machine learning techniques can be powerful analytical tools that provide new insights into the relationship between the Ki-67 index or tumor size and recurrence.

Although undifferentiated gastric cancer (UGC) diagnosed after Helicobacter pylori eradication (HPE) carries a poor prognosis, characteristics of post-HPE UGC have not been evaluated in detail because of its low incidence. Therefore, we compared the clinicopathologic characteristics of UGC and differentiated gastric cancers (DGC) diagnosed after successful HPE. GC lesions from patients who had successfully completed HPE and who had undergone upper gastrointestinal endoscopy between January 2004 and March 2016 were analyzed. Tumors were divided into DGC and UGC groups. Clinicopathologic factors of background and tumor characteristics were compared using univariate and multiple logistic analyses. A total of 129 tumors from 115 patients were evaluated; 113 tumors were in the DGC group and 16 in the UGC group. Depressed-type tumors (P = 0.024) and sub-submucosal invasion (P<0.001) were significantly higher in the UGC group. The UGC group had larger tumor diameters (25.9±7.3 mm) than the DGC group (13.2±10.2 mm) (P<0.001). Multivariate analysis showed that female sex (odds ratio [OR] 3.24, 95%CI:1.02-10.37; P = 0.047) and absent follow-up (OR 4.99, 95%CI:1.60-15.57; P = 0.006) were significant independent risk factors for UGC. The DGC group showed a gradually decreasing temporal trend by trend test (P = 0.015), while the UGC group showed a relatively constant incidence over time, although the number of cases was small. UGC was diagnosed even after long time spans following HPE, although the number of cases was small. Female sex, and especially absent follow-up, were risks for post-HPE UGC, suggesting that diligent long-term follow-up after HPE is essential.

Background: Colon capsule endoscopy (CCE) is useful as an alternative examination for patients in whom colonoscopy is difficult. The Japanese Association for Capsule Endoscopy has published a recommended regimen for CCE using castor oil, which is becoming a standard examination method for CCE in Japan. However, castor oil has an unpleasant flavor. Therefore, patient acceptance is not good. Objectives: The aims were to develop a castor oil-filled capsule and evaluate its feasibility and patient acceptance in a retrospective, comparative study. Method: A dissolution study of pig-derived gelatin capsules filled with castor oil was performed using artificial gastric juice. The CCE excretion rates within battery lifetime, CCE examination times, endoscopic colonic cleansing levels, and patient acceptability between CCE boosters with a castor oil-filled capsule and without castor oil were retrospectively compared using medical information, clinical data, and endoscopic findings at Takada Chuo Hospital from September 2016 to August 2019. Results: The castor oil-filled capsules were completely disintegrated at approximately 1–3 min in artificial gastric juice. Bowel preparation with oil-filled capsules and without castor oil was performed in 27 and 24 patients, respectively. CCE excretion rates within battery life were 100% and 91.7% (p = 0.217), small bowel transit times were 115 min and 143 min (p = 0.046), colon transit times were 168 min and 148 min (p = 0.733), and adequate colonic cleansing rates were 85.2% and 86.3% (p = 1.000) in patients using bowel preparation with and without oil-filled capsules, respectively. Regarding acceptance, the taste was not problematic in 85.2%, and tolerability for the next CCE was 96.3%. Conclusions: CCE using a castor oil-filled capsule method achieved high examination performance and sufficient patient tolerability.

INTRODUCTION:Although the rate of gastric cancer (GC) after Helicobacter pylori (H. pylori) eradication has gradually increased over time, the features of GC following eradication remain to be examined. In this study, we investigate the clinicopathological features of GC following eradication in comparison with those of GC with H. pylori infection.METHODS:50 subjects with GC following eradication [HP(-) group] and 151 patients with GC with H. pylori infection [HP(+) group] were enrolled in this study. Clinicopathological features, such as age, gender, endoscopic atrophy, tumor form, location, depth of invasion, histology, were assessed. The manifestation of GC was further evaluated using immunohistochemistry of Ki-67, CDX22, p53, claudin18, E-cadherin, c-myc and In situ hybridization for detecting Epstein-Barr virus (EBV).RESULTS:Macroscopic analysis revealed a significantly higher ratio of depressed type/elevated type in HP(-) group compared with HP(+) group (30/19 vs. 61/77, P = 0.041). Tumor size was significantly greater in HP(-) group compared with the HP(+) group (13.02 ± 7.10 vs. 16.53 ± 11.12, P = 0.0019). The gastric mucin phenotype was more predominant in HP(-) group compared with HP(+) group, and the proportion of CDX2-positive cases was lower in HP(-) group (8 out of 18; 44.4%) compared with HP(+) group (18 out of 19; 94.7%) (P = 0.00082). Ki-67 labeling index was significantly lower in HP(-) group (32.03 ± 22.15) compared with the HP(+) group (79.20 ± 14.87, P < 0.0001). No patient in HP(-) group showed significant expression of EBV infection.CONCLUSION:The clinicopathological characteristics of GC following H. pylori eradication differ from those of GC in patients with H. pylori infection in morphology, mucin phenotype, and proliferation rate. It is necessary to be careful about these differences in GC screening.

A 74‐year‐old man was diagnosed with unresectable pancreatic cancer with obstructive jaundice. Chemotherapy with gemcitabine and nab‐paclitaxel was initiated after placement of a duckbill‐shaped anti‐reflux metal stent (D‐ARMS). A period of 1 month after D‐ARMS placement, the patient developed hematemesis and entered severe shock following emergency admission for further evaluation. Contrast‐enhanced computed tomography revealed a pseudoaneurysm in the gastroduodenal artery, coincident with the site of D‐ARMS placement, and bleeding from the same site was diagnosed. Angiography was performed, and the pseudoaneurysm was successfully treated by transcatheter arterial embolization using coils. The patient was subsequently discharged from hospital and experienced no further bleeding until his death due to an aggravation of the pancreatic cancer after 2 months. We report a case of pancreatic cancer with pseudoaneurysm after D‐ARMS placement.