Aims In this study, we examine the clinicopathological and molecular features of gastric cancer (GC) with SMARCA4 alterations. Methods and results We screened SMARCA4 alterations using immunohistochemistry on 1199 surgically resected GCs with information on Epstein-Barr virus (EBV), microsatellite instability (MSI) and other SWI/SNF subunits.SMARCA4,SMARCA2andARID1Amutations were investigated by targeted sequencing. The clinicopathological significance was determined by statistical analysis. Twenty-seven cases (2%) with altered SMARCA4 expression were identified, exhibiting completely lost (six), reduced (nine) or heterogeneous (12) patterns. Frequent concomitant alterations of other SWI/SNF subunits were noted with an unusual discordant spatial heterogeneity. In comparison with SMARCA4-retained GCs, SMARCA4-lost GCs were observed more frequently in the non-EBV/MSI subgroup (five of six) and reduced or heterogeneous SMARCA4 expression mainly occurred in EBV- or MSI-associated cases (six of nine and six of 12, respectively;P < 0.001). Histologically, SMARCA4-altered GC, irrespective of expression pattern, demonstrated divergent histomorphology, spanning tubular, poorly cohesive or mixed, neuroendocrine to solid and undifferentiated carcinoma, with a predilection to the latter two (P < 0.001). De-differentiation-like transition and rhabdoid features were noted in a minority of cases. For overall survival, altered SMARCA4 expression was an unfavourable prognostic factor in stage III, EBV-associated GC and non-EBV/MSI intestinal subtype (P <= 0.001).SMARCA4orARID1Amutations were detected mainly in SMARCA4-lost or reduced GC, respectively. Conclusions SMARCA4-altered GCs are rare and have intratumoral heterogeneity, histomorphological diversity, conditional prognostic significance and various genetic drivers. SMARCA4-lost GC may represent a genuine SMARCA4-deficient neoplasm, but most SMARCA4-reduced/heterogeneous cases are secondary to ARID1A collapse or associated with different genotypes.

Aim. To improve the identification and computed tomography (CT) diagnostic accuracy of chronic active Epstein-Barr virus (EBV)-associated enteritis (CAEAE) by evaluating its CT findings and clinical manifestation.Methods.The data of three patients with pathologically and clinically confirmed CAEAE who underwent CT enterography (CTE) were retrospectively reviewed from January 2018 to October 2019. The following data were evaluated: imaging characteristics (length of involvement, pattern of mural thickening, pattern of attenuation, perienteric abnormalities), clinical symptoms, endoscopic records, laboratory examinations, and pathologic findings.Results.Based on CT findings, two patients demonstrated segmental bowel wall thickening (involvement length >6 cm), asymmetric thickening, layered attenuation, fat stranding, and adenopathy, whereas the remaining one had no positive finding. The endoscopic results of all patients showed numerous irregular ulcers in the colon, and one patient had a focal esophageal ulcer. The major clinical symptoms were abdominal pain (n=3), retrosternal pain (n=1), fever (n=3), diarrhea (n=2), hematochezia (n=1), and adenopathy (n=3). The main laboratory examination indicators were increased serum EBV DNA load (n=1) and increased inflammatory markers (n=3). With regard to the main pathologic findings, all patients showed positive EBV-encoded RNA (EBER) situ hybridization in the colonic biopsy specimen, with one patient being positive in the esophagus.Conclusion.CAEAE is rare and is usually misdiagnosed as inflammatory bowel disease (IBD). The imaging features of CAEAE overlap with those of Crohn's disease and ulcerative colitis. The presence of segmental and asymmetric bowel wall thickening, layered attenuation, and fat stranding in the CTE image may be helpful in differentiating CAEAE from IBD.