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Focal nodular hyperplasia (FNH)


Differential diagnosis and discussion: The gross image demonstrates a tan, well-circumscribed, lobulated, and grossly unencapsulated mass with a central area of fibrosis. The macroscopic findings are fairly characteristic for focal nodular hyperplasia (FNH).

FNH is a benign, non-neoplastic hepatic mass-forming lesion believed to be a response to abnormal arterial blood flow from an arteriovenous malformation. FNH is typically solitary (80%) and occurs in young women with a median age of 41-years-old. FNH is most commonly asymptomatic and discovered incidentally. The central stellate scar, as in this case, is a characteristic macroscopic feature of FNH that is seen in about 60% of cases.

The macroscopic differential diagnosis is mainly with other hepatocellular mass lesions including hepatocellular adenoma and well-differentiated hepatocellular carcinoma. It is important to evaluate the background liver when confronted with a hepatic mass lesion to determine if the mass is arising in a cirrhotic or noncirrhotic liver. FNH always occurs in the normal, noncirrhotic liver.

Hepatocellular adenoma (HCA) also occurs in the normal, noncirrhotic liver of young women with a history of oral contraceptive use. Grossly, HCAs may be solitary or multifocal, are unencapsulated, and have homogeneous cut surfaces that appear slightly different from the background hepatic parenchyma. HCAs may have hemorrhage and/or necrosis. The central scar and lobulated architecture of FNH are not seen.

Hepatocellular carcinoma (HCC) arises in the cirrhotic liver and may be solitary or multiple. Grossly, HCC may be tan, yellow, or green (due to bile production). HCC may also demonstrate hemorrhage and/or necrosis. Notably, fibrolamellar carcinoma (a rare variant of HCC) may closely resemble FNH since it occurs in the noncirrhotic liver, is multinodular, and commonly has a central scar (approximately 70% of cases).


1. Mounajjed T. Hepatocellular adenoma and focal nodular hyperplasia. Clin Liver Disease. 2021;17:244-248.
2. Susan C. Lester, Manual of Surgical Pathology, 3rd Edition. W.B. Saunders, 2010.
3. Graham RP. Fibrolamellar carcinoma: what is new and why it matters. Surgical Pathology. 2018;11:377-387.

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