Liver cancer describes a malignant growth found within the organ. To determine the true type, it is necessary to understand the tumor’s origin. The distinction lies between primary liver cancer, which begins in the liver tissues, and secondary or metastatic liver cancer, which spreads from a tumor that started elsewhere in the body. While the term “liver cancer” is often used generally, the majority of malignant tumors found in the liver are actually metastatic.
Hepatocellular Carcinoma (HCC)
Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, developing from the liver’s main functional cells, known as hepatocytes. This cancer is strongly associated with chronic liver disease, particularly cirrhosis, which is the scarring of the liver tissue. Approximately 85% of HCC cases occur in patients who already have underlying cirrhosis.
Risk factors for HCC include chronic infections with Hepatitis B and Hepatitis C viruses. Excessive alcohol consumption and non-alcoholic fatty liver disease (NAFLD), often related to obesity and type 2 diabetes, are also leading causes. HCC tumors can present either as a single dominant mass or as multiple smaller tumors scattered throughout the liver tissue. The tumor’s presentation and size are factors used in clinical staging systems to determine the appropriate treatment path.
Cholangiocarcinoma and Rare Primary Cancers
Cholangiocarcinoma is the second most common primary liver cancer. This malignancy originates in the cells lining the bile ducts, which are the tubes responsible for carrying bile from the liver to the small intestine. It is broadly categorized based on its location within the biliary system.
The intrahepatic type develops from the small bile ducts located inside the liver and is classified as a primary liver cancer. The extrahepatic type forms in the bile ducts outside the liver; it is more common but is often grouped with biliary tract cancers rather than liver cancers. Risk factors for cholangiocarcinoma include chronic inflammation of the bile ducts and certain parasitic infections.
Other forms of primary liver cancer are rare and arise from different cell types within the organ. Angiosarcoma is an aggressive cancer that develops from the endothelial cells lining the liver’s blood vessels. This malignancy is often linked to exposure to industrial chemicals, such as vinyl chloride. Hepatoblastoma is a rare cancer that primarily affects infants and children, usually diagnosed before age three. It originates from immature liver precursor cells and is the most common malignant liver tumor found in early childhood.
Metastatic Liver Cancer
Metastatic liver cancer, also known as secondary liver cancer, does not originate in the liver but spreads there from a cancer elsewhere in the body. This form of malignancy is much more common than all types of primary liver cancer combined. When cancer cells break away from the original tumor, they travel through the bloodstream or lymphatic system to the liver, forming new tumors.
The liver is a frequent destination for metastasis due to its dual and rich blood supply, which includes the hepatic artery and the portal vein. The portal vein carries blood directly from the entire gastrointestinal tract, making the liver the first major filter for cancers originating in the colon or rectum. Consequently, colorectal cancer is the most common source of liver metastases, though other primary sites include the breast, lung, and pancreas. Treatment is determined by the original location of the tumor; for example, cancer that spread from the colon is still treated as colon cancer, not primary liver cancer.