*6.1. Pseudocirrhosis*

Alterations in liver blood flow caused by VMs in HHT can lead to either di ffuse or focal hepatocellular regenerative activity, with fibrosis surrounding the abnormal vasculature [12]. On imaging, hepatic nodules and fibrosis mimic the appearance of cirrhosis. However, in HHT this appearance has been termed "pseudocirrhosis," as the normal hepatocellular architecture is preserved (Figure 7) [12,16,36]. Unlike in true cirrhosis, there is not the same increased risk of hepatocellular carcinoma (HCC) in pseudocirrhosis.

**Figure 7.** Chronic liver injury with nodular regenerative hyperplasia, pseudocirrhosis, and peripheral fibrosis in a 54-year-old woman with HHT. (**a**) Axial T1-weighted MR image shows parenchymal nodularity most prominent in the posterior right hepatic lobe (arrow). (**b**) Axial T2-weighted fat-saturated MR image shows a reticular pattern of increased signal in the posterior right hepatic lobe (arrow). (**c**) Delayed enhancement on the axial T1 fat-saturated gadolinium-enhanced MR image (arrow), along with multiple telangiectases (arrowheads).

#### *6.2. Focal Nodular Hyperplasia*

Focal nodular hyperplasia (FNH) is a common benign liver mass and represents a disorganized proliferation of hepatocytes that can occur in response to VMs. FNH has a 100-fold higher incidence in individuals with HHT [37]. Evaluation with multiphase cross-sectional imaging is usually recommended for evaluation of focal liver lesions. FNH has a highly characteristic imaging appearance on MRI, with early arterial enhancement and a T2-hyperintense "central scar" (representing disordered mixture of blood vessels and bile ducts) [29]. It is important for radiologists and clinicians to keep in mind the high incidence of FNH in HHT patients in order to avoid unnecessary biopsies.

Although FNH is benign, the imaging characteristics can pose a diagnostic dilemma, especially on a background of "pseudocirrhosis" (Figure 8). For example, lesions in HHT patients may not have the T2 hyperintense "scar [38]". In such instances, di fferentiating benign FNH from malignant HCC (or other tumors) is challenging. One solution is to obtain further imaging with gadoxetate-enhanced MRI. Gadoxetate disodium is a gadolinium-based contrast agen<sup>t</sup> that is actively taken up by hepatocytes. Because FNH is composed of proliferating hepatocytes, gadoxetate is readily taken up by these cells. Most hepatic malignant tumors (such as HCC or metastases) lack the transporter for gadoxetate, and therefore, gadoxetate remains extracellular. This results in unique imaging appearances with FNH retaining contrast (hyperintense) on the delayed "hepatobiliary phase" of gadoxetate-enhanced MRI (Figure 9), while HCC or other genuine neoplasms are usually hypointense relative to surrounding parenchyma. It is so essential to radiologically di fferentiate FNH from potential HCC due to the di fferences in management. While suspicious lesions require biopsy, a biopsy is not recommended in FNH on a background of hepatic VMs due to the bleeding risk.

**Figure 8.** Focal nodular hyperplasia (FNH) mimicking cholangiocarcinoma in a 41-year-old woman with HHT. (**a**) Pre-contrast axial T1-weighted MR image shows a focal T1 hypointense lesion in segmen<sup>t</sup> III of the left hepatic lobe (arrow). (**b**) The lesion shows restricted di ffusion at di ffusion-weighted MR imaging (arrow). (**c**) Axial T1 weighted gadolinium-enhanced MR image with fat saturation shows corresponding peripheral enhancement (arrow) as well as numerous confluent vascular masses (arrowheads). (**d**) The segmen<sup>t</sup> III lesion is hyper-enhancing on delayed phase (arrow). The confluent vascular masses are notably isointense to liver parenchyma at this phase. Ultrasound-guided biopsy of the segmen<sup>t</sup> III lesion showed features of FNH.

**Figure 9.** Focal nodular hyperplasia (FNH) in a 61-year-old woman with HHT. (**a**) Numerous hepatic lesions (arrows) are essentially imperceptible given signal characteristics similar to that of background parenchyma on pre-contrast-enhanced coronal T1-weighted MR image. (**b**) The lesions (arrows) are hyper-enhancing on the hepatobiliary phase of the gadoxetate-enhanced coronal T1-weighted MR image due to expected retention of contrast, compatible with multifocal FNH.
