Benign neoplasms of the liver must be distinguished from hepatocellular carcinoma, intrahepatic cholangiocarcinoma, and metastases (see Chapter 39). The most common benign neoplasm of the liver is the cavernous hemangioma, often an incidental finding on ultrasonography or CT (eFigure 16–42). This lesion may enlarge in women who take hormonal therapy and must be differentiated from other space-occupying intrahepatic lesions, usually by contrast-enhanced MRI, CT, or ultrasonography (eFigure 16–43). Rarely, fine-needle biopsy is necessary to differentiate these lesions and does not appear to carry an increased risk of bleeding. Surgical resection of cavernous hemangiomas is infrequently necessary but may be required for abdominal pain or rapid enlargement, to exclude malignancy, or to treat Kasabach-Merritt syndrome (consumptive coagulopathy complicating a hemangioendothelioma or rapidly growing hemangioma, usually in infants).
Hemangioma. Postcontrast CT scans demonstrate (A) early peripheral enhancement (arrow) and (B) delayed central filling (arrowhead). L, liver; S, spleen. (Reproduced, with permission, from Krebs CA, Giyanani VL, Eisenberg RL. Ultrasound Atlas of Disease Processes. Originally published by Appleton & Lange. Copyright © 1993 by The McGraw-Hill Companies, Inc.)
Hemangioma of the liver. Early post-contrast (M-7a) and late post-contrast (M-7b). Hemangiomas are the most common primary tumors of the liver, demonstrate progressive, centripetal contrast enhancement (arrows), and are uncommonly found in patients with cirrhosis. They are predominantly found in women and usually benign. (Used, with permission, from Nicholas Fidelman, MD).
In addition to rare instances of sinusoidal dilatation and peliosis hepatis, two distinct benign lesions with characteristic clinical, radiologic, and histopathologic features are focal nodular hyperplasia and hepatocellular adenoma. Focal nodular hyperplasia occurs at all ages and in both sexes and is probably not caused by oral contraceptives. It is often asymptomatic and appears as a hypervascular mass, often with a central hypodense “stellate” scar on contrast-enhanced ultrasonography, CT, or MRI (eFigure 16–44). Microscopically, focal nodular hyperplasia consists of hyperplastic units of hepatocytes that stain positively for glutamine synthetase with a central stellate scar containing proliferating bile ducts (eFigure 16–45). It is not a true neoplasm but a proliferation of hepatocytes in response to altered blood flow. Focal nodular hyperplasia is associated with an elevated angiopoietin 1/angiopoietin 2 mRNA ratio that is thought to promote angiogenesis and may also occur in patients with cirrhosis, with exposure to certain drugs such as azathioprine, and with antiphospholipid syndrome. The prevalence of hepatic hemangiomas is increased in patients with focal nodular hyperplasia.
Focal nodular hyperplasia on MRI (post-contrast). A post-contrast MRI image shows a bright, well-circumscribed hyperenhancing lesion in the right lobe of the liver that has a "central stellate scar" (arrow) without findings ...