The most common primary malignant tumor is the hepatocellular carcinoma. This commonly arises in livers with advanced chronic liver disease. Sometimes the clinical diagnosis of this condition is evident and a biopsy is not taken. Hepatocellular carcinoma can be difficult to distinguish from adenoma on biopsy, however, some histological features can aid in diagnosis. The reticulin stain is often very helpful to the pathologist because it highlights the thick cell plates and often shows loss of the normal reticulin structure.