Pathology of hepatocellular carcinoma and benign and malignant mimickers

Malignant tumors of the liver may be derived from the native liver epithelium and mesenchyma, from heterotopic tissues or metastases from any primary site imaginable. While the majority of cancers that involve the liver are metastatic, among patients with cirrhosis, hepatocellular carcinoma is actually more common. Although advances in the sensitivity and accuracy of radiographic imaging combined with other clinical parameters have significantly improved the diagnosis of most lesions, a biopsy diagnosis for confirmation remains necessary. Many benign lesions such as fibrous scars, healed granulomas, bile duct hamartoma and adenoma, and nodular hyperplasia may have a gross appearance indistinguishable from metastic carcinoma. Thus, it is imperative that every lesion suggestive of liver metastases be confirmed microscopically. The use of sophisticated imaging techniques to detect and guide the biopsy of relatively small hepatocellular nodules in patients with chronic liver disease will continue to provide diagnostic challenges. At the time of biopsy, consideration should be given to the triage of portions into fixative for electron microscopy, and frozen or fresh processing for flow cytometry, chromosome/oncogene analysis or other adjunctive studies depending on the most likely diagnostic possibilities and the availability of such analysis at a particular institution. A framework for the understanding of the salient clinicopathologic features of the more important hepatic tumors will be discussed.