Gastric cancer (GC) is the fifth most common cancer in the world and accounts for 7% of the total cancer incidence. The prognosis of GC is dismal in Western countries due to late diagnosis: approximately 70% of the patients die within 5 years following initial diagnosis. Recently, integrative genomic analyses led to the proposal of a molecular classification of GC into four subtypes, i.e.,microsatellite-instable, Epstein-Barr virus-positive, chromosomal-instable (CIN), and genomically stable GCs. Molecular classification of GC advances our knowledge of the biology of GC and may have implications for diagnostics and patient treatment. Diagnosis of microsatellite-instable GC and Epstein-Barr virus-positive GC is more or less straightforward. Microsatellite instability can be tested by immunohistochemistry (MLH1, PMS2, MSH2, and MSH6) and/or molecular-biological analysis. Epstein-Barr virus-positive GC can be tested by in situ hybridization (Epstein-Barr virus encoded small RNA). However, with regard to CIN, testing may be more complicated and may require a more in-depth knowledge of the underlying mechanism leading to CIN. In addition, CIN GC may not constitute a distinct subgroup but may rather be a compilation of a more heterogeneous group of tumors. In this review, we aim to clarify the definition of CIN and to point out the molecular mechanisms leading to this molecular phenotype and the challenges faced in characterizing this type of cancer.

中文翻译：

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胃癌生物学中的染色体不稳定。

胃癌（GC）是世界上第五大最常见的癌症，占总癌症发生率的7％。在西方国家，由于晚期诊断，GC的预后令人沮丧：大约70％的患者在初始诊断后5年内死亡。近年来，综合基因组分析提出了将GC分子分为四个亚型的建议，即微卫星不稳定，爱泼斯坦-巴尔病毒阳性，染色体不稳定（CIN）和基因组稳定的GC。GC的分子分类提高了我们对GC生物学的认识，并可能对诊断和患者治疗产生影响。诊断微卫星不稳定的GC和爱泼斯坦-巴尔病毒阳性的GC或多或少是简单的。微卫星不稳定性可以通过免疫组织化学（MLH1，PMS2，MSH2，和MSH6）和/或分子生物学分析。爱泼斯坦-巴尔病毒阳性的GC可以通过原位杂交（爱泼斯坦-巴尔病毒编码的小RNA）进行测试。但是，对于CIN，测试可能会更加复杂，并且可能需要对导致CIN的潜在机制有更深入的了解。此外，CIN GC可能不会构成一个独特的亚组，而可能是一个更加异质的肿瘤组的集合。在这篇综述中，我们旨在阐明CIN的定义，并指出导致这种分子表型的分子机制以及表征这种类型的癌症所面临的挑战。测试可能会更加复杂，并且可能需要对导致CIN的潜在机制有更深入的了解。此外，CIN GC可能不会构成一个独特的亚组，而可能是一个更加异质的肿瘤组的集合。在这篇综述中，我们旨在阐明CIN的定义，并指出导致这种分子表型的分子机制以及表征这种类型的癌症所面临的挑战。测试可能会更加复杂，并且可能需要对导致CIN的潜在机制有更深入的了解。此外，CIN GC可能不会构成一个独特的亚组，而可能是一个更加异质的肿瘤组的集合。在这篇综述中，我们旨在阐明CIN的定义，并指出导致这种分子表型的分子机制以及表征这种类型的癌症所面临的挑战。