肝癌是指发生于肝脏的恶性肿瘤。

如果是肝脏内的细胞所引发的癌病，称为“原发性肝癌”；若然是肝外的癌细胞透过血液或其他途径扩散至肝脏的话，则称为“转移性肝癌”。

原发性肝癌根据病发部位再可以细分为：

• 在肝叶的肝细胞发生的“肝细胞癌”；
• 在胆管的上皮细胞发生的“胆管细胞癌”。

原发性肝癌中有95％程度属于肝细胞癌，所以一般所讲的肝癌都专指肝细胞癌。

Liver tumors or hepatic tumors are tumors or growths on or in the liver (medical terms pertaining to the liver often start in hepato- or hepatic from the Greek word for liver, hepar). Several distinct types of tumors can develop in the liver because the liver is made up of various cell types. These growths can be benign or malignant (cancerous). They may be discovered on medical imaging (even for a different reason than the cancer itself), or may be present in patients as an abdominal mass, hepatomegaly, abdominal pain, jaundice, or some other liver dysfunction.