Diagnosis and clinical implication of collision gastric adenocarcinomas: a case report

BACKGROUND

Collision tumors are a subtype of simultaneous tumors wherein two unrelated tumors collide or infiltrate each other. Collision gastric adenocarcinomas (CGA) are rare and difficult to diagnose, and their clinical implications remain unclear. Herein, we aimed to reveal diagnostic methods for CGA and provide insight into its implications.

CASE PRESENTATION

Among 1041 cases of gastric cancers (GCs) resected between 2008 and 2018, we included cases of confirmed CGA. Patients' backgrounds, preoperative endoscopy findings, macroscopic imaging findings, and histopathology findings [including immunostaining for CK 7, MUC2, and mismatch repair (MMR) proteins] were investigated. The incidence of CGA was 0.5%: 5 of 81 cases having simultaneous multiple GCs. Tumors were mainly in the distal stomach. The CGA in two cases was between early cancers, in two cases was between early and advanced cancers, and in one case was between advanced cancers. There were three cases of collision between differentiated and undifferentiated types and two cases between differentiated types. Immunostaining with CK7 and MUC2 was useful for diagnosing collision tumor when the histology was similar to each other. Among ten GCs comprising CGA, nine tumors (90%) exhibited deficient MMR proteins, suggesting high microsatellite instability (MSI).

CONCLUSIONS

CGA is rare and usually found in the distal stomach. Close observation of shape, optimal dissection, and detailed pathological examination, including immunostaining, facilitated diagnosis. CGAs may have high MSI potential.

Robot-assisted laparoscopic total gastrectomy for Epstein-Barr virus-associated multiple gastric cancer: A case report

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It is unclear how Epstein–Barr virus causes cancer.

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EBVaGC should be considered when multiple gastric cancer is recognized.

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Robotic surgery has high-resolution three-dimensional images.

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Using forceps with multi-joint functions was effective for this case.

Introduction

Epstein–Barr virus-associated gastric cancer (EBVaGC) sometimes appears as multiple gastric cancer lesions. Here, we report a case of robot-assisted laparoscopic total gastrectomy (RTG) for a relatively rare disease with four synchronized lesions in EBVaGC and discuss the usefulness of robotic gastrectomy.

Presentation of case

A 60-year-old woman was diagnosed with multiple gastric cancer because she had five lesions in the stomach and biopsy showed the presence of adenocarcinoma in four of the five lesions. We performed robot-assisted laparoscopic total gastrectomy on the patient. The histopathological diagnosis was multiple gastric cancer T1bN0M0 pStage IA. The four lesions were positive for the Epstein–Barr virus encoding region in in-situ hybridization and were considered to be EBVaGC. The patient had no sign of recurrence without postoperative therapy for 24 months.

Disscussion

EBVaGC was found in about 10% of all gastric cancer cases worldwide. EBVaGC sometimes appears as multiple gastric cancer, suggesting that EBV infection is closely related to the early stages of tumor formation. Total gastrectomy may be necessary for multiple gastric cancer such as EBVaGC, and robotic surgery is useful in total gastrectomy in terms of high-resolution three-dimensional images and using forceps with multi-joint functions.

Conclusions

We performed RTG on a patient with four synchronous lesions of EBVaGC, which is relatively rare. Robot-assisted laparoscopic total gastrectomy is known to be a safe procedure, and we effectively performed total gastrectomy for multiple EBVaGC.

Molecular characteristics of synchronous multiple gastric cancer

Rationale: Multiple gastric cancer (MGC) is characterized by the presence of more than two different tumors in the stomach. However, the clonal relationship and carcinogenesis of MGC remain unclear. We investigated the clonal relationship and role of germline mutations in the carcinogenesis of MGC.

Methods: We gathered 16 multiple gastric cancer patients. Thirty-three tumor samples and sixteen normal gastric tissue or blood samples were obtained from January 2016 to December 2017. We also conducted analyses for 208 gastric cancer and 49 esophagogastric junction cancer (GC-EGJ) tumors from TCGA. DNA extraction from our samples was conducted for whole-exome sequencing (WES).

Results: Tumor mutation burden (TMB) was not statistically significant within database and our data in the GC-EGJ (P=0.0591) and GC groups (P=0.3113). The mutation spectrum and signatures also showed uniform distributions in GC and GC-EGJ groups within our data and TCGA database. Among sixteen patients, four were identified as monoclonal, in which 11, 10, 26 and 6 somatic mutations were shared within different tumors of P7, P8, P9 and P16, respectively. However, no common mutation between different tumors of the same patient was found among the other 12 patients. After identifying predisposing genes, we found that germline MSH2 and NCOR2 mutations were significantly dominant in 8/12 and 10/12 of genetic MGC patients. Additionally, all patients were identified with MSH2 mutations in cancer samples of those genetic MGC patients. Taking genetic MGCs as a whole, we identified that TP53 were significantly mutated in 14 of 25 tumor samples.

Main conclusions: WES analyses are suggestive of monoclonal and polyclonal origin of MGC, which may promote the classification of MGC into genetic and metastatic MGC. For patients with genetic MGC, germline MSH2 X314_splice variants may contribute to carcinogenesis, thus prompting the consideration of more radical surgery and/or anti-PD-1/PD-L1 therapy.

Clinicopathological features and impact of adjuvant chemotherapy on the long-term survival of patients with multiple gastric cancers: a propensity score matching analysis

Background

Little is known about the correlation between the clinicopathological features, postoperative treatment, and prognosis of multiple gastric cancers (MGCs). In this study, we aimed to investigate the correlation between these features and the impact of postoperative adjuvant chemotherapy on the long-term survival of patients with MGC.

Methods

The clinical and pathological data of patients diagnosed with gastric adenocarcinoma who had radical gastrectomy from January 2007 to December 2016 were analyzed. Using propensity score matching, the prognostic differences, and the impact of postoperative adjuvant chemotherapy between those with MGC and solitary gastric cancers (SGC) were compared.

Results

Among the 4107 patients investigated, the incidence of MGC was 3.2% (133/4107). Before matching, patients with MGC and SGC had disparities in the type of gastrectomy, pathological tumor stage (pT), pathological node stage (pN), and pathological tumor-node-metastasis stage (pTNM). After a 1:4 ratio matching, the clinical data of 133 cases of MGC and 532 cases of SGC were found to be comparable. The 5-year overall survival (OS) rate was 56.6% in the entire matched cohort, 48.1% in the MGC group, and 58.7% in the SGC group (P = 0.013). Multivariate analysis revealed that MGC, age, pT stage, pN stage, and adjuvant chemotherapy were independent predictors of OS (all P < 0.05). Stratified analyses demonstrated that for the cohort of advanced gastric cancer (AGC) patients who did not had adjuvant chemotherapy, the 5-year OS rate of advanced cases of MGC was inferior than that of SGC patients (34.0% vs. 46.1%, respectively; P = 0.025) but there were no significant difference in the 5-year OS rate between advanced MGC and SGC patients who had adjuvant chemotherapy (48.0% vs. 53.3%, respectively; P = 0.292). Further, we found that the 5-year OS rate of advanced MGC who had adjuvant chemotherapy was significantly higher than those who did not had adjuvant chemotherapy (48.0% vs. 34.0%, P = 0.026).

Conclusions

Patients with advanced MGC was identified as having a poorer survival as to SGC patients, but the implementation of postoperative adjuvant chemotherapy showed that it had the potential to significantly improve the long-term prognoses of MGC patients.