Steatohepatitis-like Changes in Focal Nodular Hyperplasia, A Finding to Distinguish From Steatohepatitic Variant of Hepatocellular Carcinoma.

Steatohepatitis-like change has not been described in focal nodular hyperplasia (FNH). Steatohepatitis-like change in FNH may show overlapping features with steatohepatitic variant of hepatocellular carcinoma (HCC). This problem can be compounded if seen in FNH with widened cell plates or hepatocyte rosettes, other features that can also be seen in HCC. This study examined steatotic FNHs for the frequency of steatohepatitis-like change, especially in the setting of FNH with rosettes and/or widened cell plates. Thirty-three resection specimens of steatotic FNH from 3 institutions were evaluated for degree of steatosis, background liver steatosis, ductular reaction, and lymphocytic infiltrate, as well as presence of thick fibrous bands, thick-walled vessels, ballooned hepatocytes, Mallory-Denk bodies, dilated sinusoids, hepatocyte rosettes, and thick hepatic plates. Steatosis was distributed along fibrous septa as well as diffusely throughout the FNH. Steatohepatitis-like changes were focally present in 54% (18 cases). Thick plates>3 cells were focally found in 14 cases (42%); rosettes were common (70%). All cases showed at least 2 of the histologic features highly suggestive for the diagnosis of FNH such as thick bands of fibrosis, thick-walled vessels and/or ductular reaction and the typical map-like pattern of glutamine synthetase immunostaining. More than half of fatty FNH examined for this study had features of at least focal steatohepatitis-like changes. This finding should not be confused with steatohepatitic variant of HCC. Common typical features of FNH including thick-walled vessels, ductular reaction and thick fibrous bands are helpful for discrimination of FNH from HCC.