Background: Gastric cancer (GC) is a common malignant tumor with a high incidence in China. The use of immune checkpoint inhibitors has become the focus of tumor immunotherapy in recent years. This study was to investigate the clinicopathological and prognostic significance of programmed death ligant-1 (PD-L1) expression in GC. Methods: We searched the PubMed, ScienceNet, EMbase, CNKI, and Wanfang databases for retrospective cohort studies on the clinicopathology and prognosis of PD-L1 expression in GC published between January 2010 and April 2020. The literature was first selected to extract data according to the inclusion and exclusion criteria, then a meta-analysis performed using Stata15.0 software. Publication bias and sensitivity analysis were carried out for the included studies. Results: A total of 3,218 patients in 15 studies were included in the meta-analysis. The positive expression of PD-L1 was related to a decrease in the 3-year survival rate (HR =1.32, 95% CI: 1.02-1.49, P=0.028) and 5-year survival rate (HR =1.39, 95% CI: 1.14-1.69, P=0.001). The difference in PD-L1 expression was related to lymph node metastasis (OR =1.73, 95% CI: 1.18-2.54, P<0.001), but not to tumor stage (OR =1.28, 95% CI: 0.81-2.02, P=0.292). Conclusions:The results show that PD-L1 is related to the prognosis of GC. Its high expression decreases the 3-and 5-year survival rates and promotes lymph node metastasis, but does not reflect tumor stage. The results may provide a theoretical basis for the choice of clinical immunotherapy in GC patients.

Gastric cystica profunda (GCP) is a rare disease characterized by multiple cystic lesions in the mucosa and/or submucosal layer. Usually, GCP occurs in stomachs that have previously been operated on.If there is no postoperative pathological results, it is challenging to diagnose GCP based on nonspecific clinical symptoms and imaging findings. This report aimed to provide a comprehensive overview of all cases of GCP reported to date. A comprehensive literature search was conducted for all reported GCP cases between 1972 and 2014. The keywords searched included "gastritis cystica profunda", "submucosal cysts of the stomach", and "heterotopic submucosal gastric glands". One retrospective case from our group was also reported and compared with those from the existing literature. A total of 52 cases were found including 37 (71.2%) men and 15 (28.8%) women (M/F ratio =2.5). The mean age of the patients was 59.9 (range, 39-91) years old. Among the cases, 58.8% (n=30) of lesions were located in the gastric body, 25.5% (n=13) of lesions were located in the fundus, 19.6% (n=9) of lesions were located in the antrum, and 3.9% (n=2) of lesions were located in the cardia, while 1 case was in the prepyloric lesion and 1 case was at the anastomotic site. Of the patients, 52% (n=26) had previously received gastric surgery. The main manifestations of GCP included abdominal pain (n=14, 36.8%) and gastrointestinal bleeding (including hematemesis and melena, n=7, 18.4%). Only 4 of the 52 cases were diagnosed before surgery, and the rest were diagnosed through postoperative histopathologic examination. GCP is difficult to correctly diagnose preoperatively due to its relative rarity and lack of typical clinical symptoms. Histopathological examination should be used for correct diagnosis. Complete surgical removal of the GCP is widely considered as the best treatment option.

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