Review of the clinicopathologic features of fibrolamellar carcinoma.

Since its first description 50 years ago, fibrolamellar carcinomas (FLCs) have been recognized as a unique type of primary liver cancer. FLCs occur principally in children and young adults and are not associated with chronic liver disease. Their etiology is unknown. The tumor is made up of large polygonal cells containing abundant eosinophilic cytoplasm, large vesiculated nuclei, and large nucleoli, with tumor cells that are embedded in lamellar bands of fibrosis. Although rare, the most common variant of FLC shows areas of glandular type differentiation with mucin production. The uniqueness of FLC extends to their molecular findings, as they show no evidence for involvement by many of the major pathways and genes that are dysregulated in typical hepatocellular carcinoma, including alpha-fetoprotein, TP53 mutations, and beta catenin mutations. FLCs are not indolent tumors, but have an overall better prognosis than hepatocellular carcinomas of the usual sort because of the younger age at presentation and lack of cirrhosis. The most important prognostic feature is resectability. Although their morphologic appearance on routine stains is well defined, their etiology is still unknown and much of their molecular biology remains poorly described and awaits future investigation.