Human Epidermal Growth Factor Receptor 2-Positive, Claudin-18 Isoform 2-Positive, Mismatch Repair-Deficient Gastric Cancer Revealed by Immunohistochemical Analysis of Surgical Specimens: A Case Report

IF 2.5 Q4 ONCOLOGY

Cancer reports Pub Date : 2026-08-06 DOI:10.1002/cnr2.70646

Daichi Takagi, Mikito Mori, Kiyohiko Shuto, Chihiro Kosugi, Akihiro Usui, Ryosuke Takayanagi, Shunsuke Sato, Sumiyo Adachi, Takashi Fujino, Kazuto Yamazaki, Hiroaki Shimizu

{"title":"Human Epidermal Growth Factor Receptor 2-Positive, Claudin-18 Isoform 2-Positive, Mismatch Repair-Deficient Gastric Cancer Revealed by Immunohistochemical Analysis of Surgical Specimens: A Case Report","authors":"Daichi Takagi, Mikito Mori, Kiyohiko Shuto, Chihiro Kosugi, Akihiro Usui, Ryosuke Takayanagi, Shunsuke Sato, Sumiyo Adachi, Takashi Fujino, Kazuto Yamazaki, Hiroaki Shimizu","doi":"10.1002/cnr2.70646","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Background</h3>\n \n <p>Human epidermal growth factor receptor 2 (HER2), mismatch repair (MMR) proteins, claudin-18 isoform 2 (CLDN18.2), and the programmed cell death ligand-1 combined positive score (PD-L1 CPS) are predictive biomarkers for the efficacy of combination chemotherapy in patients with locally advanced unresectable or metastatic gastric or gastroesophageal junction cancer. However, only a small proportion of these patients are positive for at least two of these predictive biomarkers.</p>\n </section>\n \n <section>\n \n <h3> Case</h3>\n \n <p>We present a rare case of HER2-positive, CLDN18.2-positive, MMR-deficient gastric cancer. A 72-year-old man was initially diagnosed with clinical stage IVB gastric cancer (cT4aN0, M1 PUL). Immunohistochemical analysis of endoscopic biopsy specimens revealed HER2-negative, CLDN18.2-negative, and MMR-proficient gastric cancer. He underwent surgery to remove the hemorrhagic gastric cancer before chemotherapy, and immunohistochemical analysis of surgical specimens revealed HER2-positive, CLDN18.2-positive, and MMR-deficient gastric cancer. Moreover, a transbronchial lung biopsy after surgery showed that one of the bilateral multiple lung nodules was lung adenocarcinoma, and he was ultimately diagnosed with pathological stage IIB gastric cancer and clinical stage IVB lung cancer. He died of lung cancer without any signs of gastric cancer recurrence during 17 months of follow-up.</p>\n </section>\n \n <section>\n \n <h3> Conclusion</h3>\n \n <p>HER2-positive, CLDN18.2-positive, MMR-deficient gastric cancer is extremely rare. Adequate endoscopic biopsy sampling from different areas of a tumor is essential for accurate predictive biomarker assessment in patients with gastric or gastroesophageal junction cancer because of intratumoral heterogeneity.</p>\n </section>\n </div>","PeriodicalId":9440,"journal":{"name":"Cancer reports","volume":"9 8","pages":""},"PeriodicalIF":2.5000,"publicationDate":"2026-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13447005/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cancer reports","FirstCategoryId":"1085","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/cnr2.70646","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"ONCOLOGY","Score":null,"Total":0}

引用次数: 0

Abstract

Background

Human epidermal growth factor receptor 2 (HER2), mismatch repair (MMR) proteins, claudin-18 isoform 2 (CLDN18.2), and the programmed cell death ligand-1 combined positive score (PD-L1 CPS) are predictive biomarkers for the efficacy of combination chemotherapy in patients with locally advanced unresectable or metastatic gastric or gastroesophageal junction cancer. However, only a small proportion of these patients are positive for at least two of these predictive biomarkers.

Case

We present a rare case of HER2-positive, CLDN18.2-positive, MMR-deficient gastric cancer. A 72-year-old man was initially diagnosed with clinical stage IVB gastric cancer (cT4aN0, M1 PUL). Immunohistochemical analysis of endoscopic biopsy specimens revealed HER2-negative, CLDN18.2-negative, and MMR-proficient gastric cancer. He underwent surgery to remove the hemorrhagic gastric cancer before chemotherapy, and immunohistochemical analysis of surgical specimens revealed HER2-positive, CLDN18.2-positive, and MMR-deficient gastric cancer. Moreover, a transbronchial lung biopsy after surgery showed that one of the bilateral multiple lung nodules was lung adenocarcinoma, and he was ultimately diagnosed with pathological stage IIB gastric cancer and clinical stage IVB lung cancer. He died of lung cancer without any signs of gastric cancer recurrence during 17 months of follow-up.

Conclusion

HER2-positive, CLDN18.2-positive, MMR-deficient gastric cancer is extremely rare. Adequate endoscopic biopsy sampling from different areas of a tumor is essential for accurate predictive biomarker assessment in patients with gastric or gastroesophageal junction cancer because of intratumoral heterogeneity.

查看原文本刊更多论文

人表皮生长因子受体2阳性，cladin -18亚型2阳性，手术标本免疫组化分析发现错配修复缺陷胃癌1例

背景：人表皮生长因子受体2 （HER2）、错配修复（MMR）蛋白、CLDN18.2和程序性细胞死亡配体-1联合阳性评分（PD-L1 CPS）是局部晚期不可切除或转移性胃癌或胃食管结癌患者联合化疗疗效的预测性生物标志物。然而，这些患者中只有一小部分在至少两种预测性生物标志物上呈阳性。病例：我们报告一例罕见的her2阳性，cldn18.2阳性，mmr缺陷胃癌。一名72岁男性最初被诊断为临床IVB期胃癌（cT4aN0, M1 PUL）。内镜活检标本的免疫组化分析显示her2阴性，cldn18.2阴性，mmr精通胃癌。化疗前行手术切除出血性胃癌，手术标本免疫组化分析显示her2阳性、cldn18.2阳性、mmr缺失胃癌。术后经支气管肺活检显示双侧多发肺结节之一为肺腺癌，最终病理诊断为IIB期胃癌，临床诊断为IVB期肺癌。随访17个月，患者死于肺癌，无胃癌复发迹象。结论：her2阳性、cldn18.2阳性、mmr缺陷型胃癌极为罕见。由于肿瘤内的异质性，从肿瘤的不同区域进行足够的内镜活检取样对于胃癌或胃食管结癌患者准确的预测性生物标志物评估至关重要。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊