一个多世纪以前，科学家们就首次发现了肿瘤区域中细菌的存在。但是，微生物在肿瘤发生中的作用近年来才被认识到。近几十年来，与肠道菌群失调相关的疾病代表了全世界最严重的一些公共卫生问题。大量的流行病学研究表明，肠道菌群与某些常见肿瘤密切相关。然而，肠道菌群与肿瘤相关联的具体分子机制仍不明确。研究表明，肠道菌群的改变有助于确定肝癌、酒精相关肝病、非酒精性脂肪肝和肝硬化的发生和发展。鉴于益生菌是一种可通过调节免疫系统促进人类健康的药物，其可能会为肝细胞癌(HCC) 和非酒精性脂肪肝的治疗提供新方向。本文总结了肠道菌群在肿瘤及肝病中的研究进展，综述了肠道菌群与肿瘤和肝病之间的关系。此外，考虑到细菌内稳态的重要性，我们也对益生菌进行了概述，旨在为相关疾病的治疗提供指导。

In recent decades, diseases concerning the gut microbiota have presented some of the most serious public health problems worldwide. The human host's physiological status is influenced by the intestinal microbiome, thus integrating external factors, such as diet, with genetic and immune signals. The notion that chronic inflammation drives carcinogenesis has been widely established for various tissues. It is surprising that the role of the microbiota in tumorigenesis has only recently been recognized, given that the presence of bacteria at tumor sites was first described more than a century ago. Extensive epidemiological studies have revealed that there is a strong link between the gut microbiota and some common cancers. However, the exact molecular mechanisms linking the gut microbiota and cancer are not yet fully understood. Changes to the gut microbiota are instrumental in determining the occurrence and progression of hepatocarcinoma, chronic liver diseases related to alcohol, nonalcoholic fatty liver disease (NAFLD), and cirrhosis. To be specific, the gut milieu may play an important role in systemic inflammation, endotoxemia, and vasodilation, which leads to complications such as spontaneous bacterial peritonitis and hepatic encephalopathy. Relevant animal studies involving gut microbiota manipulations, combined with observational studies on patients with NAFLD, have provided ample evidence pointing to the contribution of dysbiosis to the pathogenesis of NAFLD. Given the poor prognosis of these clinical events, their prevention and early management are essential. Studies of the composition and function of the gut microbiota could shed some light on understanding the prognosis because the microbiota serves as an essential component of the gut milieu that can impact the aforementioned clinical events. As far as disease management is concerned, probiotics may provide a novel direction for therapeutics for hepatocellular carcinoma (HCC) and NAFLD, given that probiotics function as a type of medicine that can improve human health by regulating the immune system. Here, we provide an overview of the relationships among the gut microbiota, tumors, and liver diseases. In addition, considering the significance of bacterial homeostasis, we discuss probiotics in this article in order to guide treatments for related diseases.