How Do I Diagnose Fibrolamellar Carcinoma?

Fibrolamellar carcinoma (FLC) is a unique primary carcinoma of liver that is characterized by distinct morphologic findings and a recurrent DNAJB1::PRKACA gene fusion. It typically presents in young individuals without underlying liver dysfunction. FLC is a difficult diagnosis when based only on morphology and misdiagnosis is not uncommon. Frequent differential diagnoses include conventional hepatocellular carcinoma and intrahepatic cholangiocarcinoma, both of which can show similar morphologic and immunohistochemical features. If based only on molecular analysis other differential diagnoses have recently emerged, as the DNAJB1::PRKACA fusion has now been reported in cases of intraductal oncocytic papillary neoplasm and intraductal papillary mucinous neoplasm. In this article we review our diagnostic approach to FLC, which relies on both morphologic and immunohistochemical features, as well as molecular analysis.