*6.1.3.3 Classification of HAs based on imaging examinations*

MRI is the imaging modality of choice for characterization of HA subtypes [22]. Inflammation, abnormal rich vascularization, peliotic areas, and abundant fatty infiltration are pathologic findings differently present in the HA subtypes at multiparametric MRI [41].

*HNF1A-mutated adenoma (H-HA):* on MRI, the diffuse and homogenous fat deposition within HA-H determines a specific imaging pattern: on T1-weighted Gradient-Echo MR, it is hyper- or isointense, with diffuse signal drop-off with the use of chemical shift sequence (**Figure 17**). On T2-weight MR, images appears isointense to slightly hyperintense. Gadolinium-enhanced T1-weighted MR images show moderate enhancement in the arterial phase, with no persistent enhancement in the portal venous and delayed phases. Generally, its size is less than 5 cm, and there are minimal risks of bleeding and malignant transformation [22]. At multidetector CT, macroscopic fat deposits can be identified and establish the diagnosis of H-HA. On CEUS, it has iso- to moderately increased vascularity, mixed filling in the arterial phase after contrast and isoechoic appearance in the portal venous and delayed phases.

*β-catenin-mutated hepatic adenoma (β-HA):* there are no distinctive patterns established on MRI, multidetector CT, or CEUS, but they usually are hypervascular with evidence of hemorrhage or necrosis within tumor. Besides the fact that has the highest risk of malignant transformation (> 10%), it may mimic hepatocellular carcinoma with strong enhancement during arterial phase and with portal venous wash-out.

*Inflammatory hepatic adenoma (IHA):* includes those previously called "telangiectatic HA." It has specific patterns on MRI due to less fat content, sinusoidal dilation, peliotic areas, and abnormal vessels. On T1-weighted Gradient-Echo MR images, it is depicted as isointense or mildly hyperintense, without signal drop-off with the use of chemical sequence, and on T2-weighted MR images, it becomes bright (diffusely hyperintense). On Gadolinium-enhanced T1-weighted MR images, it shows intense enhancement during arterial phase that persists in

#### **Figure 17.**

*HNF1A-mutated HA: diffuse lipid deposition within HA best seen using T1 with TE in and out of phase (arrow).*

**133**

specificity [46].

**Figure 18.**

**6.2 Nuclear medicine studies**

*Challenging Issues in Hepatic Adenoma DOI: http://dx.doi.org/10.5772/intechopen.87993*

wash-out in the late venous phase.

*and discreetly hyperintense in portal and late phase.*

*6.1.3.4 Differential imaging diagnostic of adenomas*

Vascular, biliary invasion and metastases are common.

the portal venous and delayed phases (**Figure 18**). The atoll sign is specific for IHA and may be due to sinusoidal dilatation. In up to 30% of cases, there is evidence of hemorrhage, and a 10% likelihood of malignant degeneration is estimated. At multidetector CT, IHA is depicted as heterogeneously hyperattenuating mass in NECT and in CECT shows enhancement features similar to those at MRI. At CEUS, it has arterial vascularity with centripetal filling, a sustained enhanced rim and central

*Inflammatory liver adenoma: hyperintensity T2 wi and hypervascularity of the liver mass through the late AP,* 

*Unclassified hepatic adenoma (U-HA)* does not fit other profiles of HA subtypes.

*Fibrolamellar HCC* is shown as a large, lobulated mass with scar and septa inside.

*Hypervascular metastases* are usually multiple. The primary tumor (i.e., thyroid, breast, kidney, or endocrine) must be searched for. CT + C or MRI + C in arterial phase shows heterogeneous enhancement. In portal and delayed phases, hypervas-

Most HAs have a decreased uptake of Gallium and colloid, early and retained

If radiological studies cannot distinguish HA from HCC and FNH, a combination of radionuclide imaging, including technetium (99mTc)-sulfur colloid sulfur-colloid,

cular metastases may appear isodense, hypodense, or hypointense.

uptake of hepatobiliary agents, and no uptake on PET scanning.

*Hepatocellular carcinoma (HCC)* may be hard to distinguish on imaging or pathology. Biliary, vascular, nodal invasion and metastases of HCC typically occur in older, cirrhotic men [42, 45]. Adenoma occurs in young, healthy women.

*Focal nodular hyperplasia (FNH)* is depicted on MRI + C in arterial phase as a homogeneously enhancing mass and in all other phases as an isodense mass comparative to normal liver. In T2WI, a scar is typically seen as hyperintense. On delayed phase MR, FNH uniformly retains Gadoxetate [44, 45]. Gadoxetic acidenhanced MRI can differentiate between HA and FNH with a high sensitivity and

**Figure 18.**

*Liver Disease and Surgery*

of malignant transformation [42].

multiparametric MRI [41].

delayed phases.

wash-out.

MRI with hepatobiliary agents is an important tool not only in differential subtype definition but even in surveillance with early identification of complications and discovery of some signs of HA malignant degeneration [41]. Lesion enlargement and heterogeneity of signal intensity and of contrast enhancement are signs

*Imaging recommendations*: the best imaging tool is represented by Gadoxetateenhanced MRI including multiphase and hepato-biliary phase acquisition [43]. The

MRI is the imaging modality of choice for characterization of HA subtypes [22]. Inflammation, abnormal rich vascularization, peliotic areas, and abundant fatty infiltration are pathologic findings differently present in the HA subtypes at

*HNF1A-mutated adenoma (H-HA):* on MRI, the diffuse and homogenous fat deposition within HA-H determines a specific imaging pattern: on T1-weighted Gradient-Echo MR, it is hyper- or isointense, with diffuse signal drop-off with the use of chemical shift sequence (**Figure 17**). On T2-weight MR, images appears isointense to slightly hyperintense. Gadolinium-enhanced T1-weighted MR images show moderate enhancement in the arterial phase, with no persistent enhancement in the portal venous and delayed phases. Generally, its size is less than 5 cm, and there are minimal risks of bleeding and malignant transformation [22]. At multidetector CT, macroscopic fat deposits can be identified and establish the diagnosis of H-HA. On CEUS, it has iso- to moderately increased vascularity, mixed filling in the arterial phase after contrast and isoechoic appearance in the portal venous and

*β-catenin-mutated hepatic adenoma (β-HA):* there are no distinctive patterns established on MRI, multidetector CT, or CEUS, but they usually are hypervascular with evidence of hemorrhage or necrosis within tumor. Besides the fact that has the highest risk of malignant transformation (> 10%), it may mimic hepatocellular carcinoma with strong enhancement during arterial phase and with portal venous

*Inflammatory hepatic adenoma (IHA):* includes those previously called "telangiectatic HA." It has specific patterns on MRI due to less fat content, sinusoidal dilation, peliotic areas, and abnormal vessels. On T1-weighted Gradient-Echo MR images, it is depicted as isointense or mildly hyperintense, without signal drop-off with the use of chemical sequence, and on T2-weighted MR images, it becomes bright (diffusely hyperintense). On Gadolinium-enhanced T1-weighted MR images, it shows intense enhancement during arterial phase that persists in

*HNF1A-mutated HA: diffuse lipid deposition within HA best seen using T1 with TE in and out of phase* 

best sequence to evaluate fat into HA is T1wi with in and opposed TE.

*6.1.3.3 Classification of HAs based on imaging examinations*

**132**

**Figure 17.**

*(arrow).*

*Inflammatory liver adenoma: hyperintensity T2 wi and hypervascularity of the liver mass through the late AP, and discreetly hyperintense in portal and late phase.*

the portal venous and delayed phases (**Figure 18**). The atoll sign is specific for IHA and may be due to sinusoidal dilatation. In up to 30% of cases, there is evidence of hemorrhage, and a 10% likelihood of malignant degeneration is estimated. At multidetector CT, IHA is depicted as heterogeneously hyperattenuating mass in NECT and in CECT shows enhancement features similar to those at MRI. At CEUS, it has arterial vascularity with centripetal filling, a sustained enhanced rim and central wash-out in the late venous phase.

*Unclassified hepatic adenoma (U-HA)* does not fit other profiles of HA subtypes.
