Malignant tumors of the liver are primarily adenocarcinomas, with two major cell types: hepatocellular and cholangiocarcinoma.

Histologic classification is as follows:

• Hepatocellular carcinoma (liver cell carcinoma).
• Hepatocellular carcinoma (fibrolamellar variant).  [Note: The fibrolamellar variant is important because an increased proportion of these patients may be cured if the tumor can be resected. It is more frequent in young women. It also generally exhibits a slower clinical course than the more common hepatocellular carcinoma.]
• Cholangiocarcinoma (intrahepatic bile duct carcinoma).
• Mixed hepatocellular cholangiocarcinoma.
• Undifferentiated.

Hepatoblastoma rarely occurs in adults.