Inflammatory hepatocellular adenomas can mimic focal nodular hyperplasia on gadoxetic acid-enhanced MRI. AJR Am J Roentgenol. 2014;203:W408-W414. [PMID: 25055198 DOI: 10.2214/ajr.13.12251]

Malignant Transformation of Hepatic Adenoma in Glycogen Storage Disease Type-1a: Report of an Exceptional Case Diagnosed on Surveillance Imaging

Hepatocellular adenoma is a heterogeneous group of benign neoplasms arising from hepatocellular cells and can be subclassified into four major groups based on genotypic and phenotypic characteristics. These four subtypes are hepatocyte nuclear factor (HNF) 1α-inactivated, β-catenin–activated, inflammatory, and unclassified adenomas. Immunohistochemistry studies have demonstrated that since β-catenin–activated adenomas have a higher risk of malignant transformation, the identification of the subtype of adenoma remains crucial in patient management. However, malignant transformation of hepatic adenoma without β-catenin overexpression can be seen in 30–65% cases. We report a case of malignant transformation of hepatic adenoma without overexpression of β-catenin in a 31-year-old man with a known glycogen storage disease (GSD) Type-1a, which was diagnosed on surveillance magnetic resonance imaging (MRI). The MRI showed a mild interval increase in one lesion with relative stability of the other adenomas. The lesion was presumed to be suspicious for a hepatocellular carcinoma (HCC) and was confirmed on pathology.

Focal Nodular Hyperplasia and Hepatocellular Adenoma: Accuracy of Gadoxetic Acid-enhanced MR Imaging--A Systematic Review

PURPOSE

To perform a systematic review to evaluate the diagnostic accuracy of hepatobiliary (HPB) phase gadoxetic acid-enhanced MR imaging of the liver in the diagnosis of focal nodular hyperplasia (FNH) versus hepatocellular adenoma (HCA) and to identify the rate of (a) reported HCAs that are iso- or hyperintense to liver and (b) reported FNHs that are hypointense to liver on HPB phase MR images.

MATERIALS AND METHODS

The institutional review board granted a waiver for this study type, and multiple databases were searched for studies in which researchers distinguished between FNH and HCA with gadoxetic acid-enhanced MR imaging. Studies to evaluate diagnostic accuracy were included; case reports and series were included to analyze the rate of iso- or hyperintense HCAs on HPB phase MR images. Risk of bias was assessed by using the Quality Assessment Tool for Diagnostic Accuracy Studies-2. Sensitivity and specificity were plotted with a forest plot; pooling was not performed because a small number of heterogeneous studies were included. Rate of iso- or hyperintense HCA on HPB phase gadoxetic acid-enhanced MR images was evaluated.

RESULTS

Six studies (309 patients; 164 with HCA, 233 with FNH) were included for diagnostic accuracy assessment. Twelve case series (129 patients; 81 with HCA, 70 with FNH) were included (studies with insufficient 2 × 2 table data for diagnostic accuracy assessment). Sensitivity was high (range, 0.91-1.00; lower margin of the 95% confidence interval: 0.77). Specificity was high (range, 0.87-1.00; lower margin of the 95% confidence interval: 0.54). Specificity was lowest among studies in which molecular subtyping of HCA was performed. Rate of iso-or hyperintensity of HCA on HPB phase MR images was variable (range, 0%-67%) and occurred more frequently in the inflammatory subtype. High risk of bias was identified in the domains of patient selection and reference standard.

CONCLUSION

The reported diagnostic accuracy of HPB phase gadoxetic acid-enhanced MR imaging in the diagnosis of HCA versus FNH is high; however, studies are few, heterogeneous, and at high risk for bias, indicating that diagnostic accuracy may be overestimated.

Morphologic and Molecular Features of Hepatocellular Adenoma with Gadoxetic Acid-enhanced MR Imaging

PURPOSE

To evaluate the diagnostic performance of imaging features of gadoxetic acid-enhanced magnetic resonance (MR) imaging to differentiate among hepatocellular adenoma (HCA) subtypes by using the histopathologic results of the new immunophenotype and genotype classification and to correlate the enhancement pattern on the hepatobiliary phase (HBP) with the degrees of expression of organic anion transporting polypeptide (OATP1B1/3), multidrug resistance-associated protein 2 (MRP) (MRP2), and MRP 3 (MRP3) transporters.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and the requirement for informed consent waived. MR imaging findings of 29 patients with 43 HCAs were assessed by two radiologists independently then compared with the histopathologic analysis as the standard of reference. Receiver operating characteristic curves and Spearman rank correlation coefficient were used to test the diagnostic performance of gadoxetic acid-enhanced MR imaging features, which included the retention or washout at HBP and degree of transporter expression. Interreader agreement was assessed by using the κ statistic with 95% confidence interval.

RESULTS

The area under the curve for the diagnosis of inflammatory HCA was 0.79 (95% confidence interval: 0.64, 0.90); for the steatotic type, it was 0.90 (95% confidence interval: 0.77, 0.97); and for the β-catenin type, it was 0.87 (95% confidence interval: 0.74, 0.95). There were no imaging features that showed a significant statistical correlation for the diagnosis of unclassified HCAs. On immunohistochemical staining, OATP1B1/3 expression was the main determinant for the retention, whereas MRP3 was the key determinant for washout of gadoxetic acid at HBP (P < .001). MRP2 appeared to have no role.

CONCLUSION

Gadoxetic acid-enhanced MR imaging features may suggest the subtype of HCA. The degree of OATP1B1/3 and MRP3 expression correlated statistically with gadoxetic acid retention and washout, respectively, in the HBP.

Differentiation of focal nodular hyperplasia from hepatocellular adenoma: Role of the quantitative analysis of gadobenate dimeglumine-enhanced hepatobiliary phase MRI

PURPOSE

To determine the value of quantitative analysis of the hepatobiliary phase (HBP) in gadobenate dimeglumine (Gd-BOPTA)-enhanced magnetic resonance imaging (MRI) to differentiate focal nodular hyperplasia (FNH) from hepatocellular adenoma (HCA).

MATERIALS AND METHODS

Thirty-eight patients bearing 67 lesions (40 FNH; 27 HCA) were retrospectively included in this Institutional Review Board-approved study. The same volumetric interpolated breath-hold examination (VIBE) T1 -weighted sequences were performed before and after contrast injection on a 1.5T MRI, with HBP images acquired with a mean delay of 80 minutes (range 60-120 min). After a visual assessment of lesions enhancement (qualitative HBP analysis), the HBP signal intensity ratio (SIR) and the lesion-to-liver contrast enhancement ratio (LLCER) were calculated for each lesion by two observers (Mann-Whitney test). The sensitivities, specificities (receiver operating characteristic [ROC] curve analysis) and interobserver correlation (intraclass coefficient, ICC) of quantitative HBP analysis were determined.

RESULTS

All FNH and 44.4% of HCA appeared hyper- or isointense relative to the adjacent liver on qualitative HBP analysis. The mean SIR (P < 0.01) and LLCER (P < 0.0001) of FNH were significantly higher than that of HCA. The area under the ROC curve for the differentiation of FNH from HCA with LLCER was 0.98 for both observers. With a cutoff value of -0.3%-observer 1 with highest experience- LLCER assessment provided respective sensitivity and specificity values of 100% and 96.2% for the differentiation of FNH from HCA. The ICC was 0.7 for SIR measurements and 0.8 for LLCER measurements.

CONCLUSION

Quantitative LLCER assessment allows an accurate differentiation of FNH from HCA, even in hyper- or isointense HCA on HBP images.

Current updates on the molecular genetics and magnetic resonance imaging of focal nodular hyperplasia and hepatocellular adenoma

Focal nodular hyperplasia (FNH) and hepatocellular adenomas (HCAs) constitute benign hepatic neoplasms in adults. HCAs are monoclonal neoplasms characterised by an increased predilection to haemorrhage and also malignant transformation. On the other hand, FNH is a polyclonal tumour-like lesion that occurs in response to increased perfusion and has an uneventful clinical course. Recent advances in molecular genetics and genotype-phenotype correlation in these hepatocellular neoplasms have enabled a new classification system. FNHs are classified into the typical and atypical types based on histomorphological and imaging features. HCAs have been categorised into four subtypes: (1) HCAs with HNF-1α mutations are diffusely steatotic, do not undergo malignant transformation, and are associated with familial diabetes or adenomatosis. (2) Inflammatory HCAs are hypervascular with marked peliosis and a tendency to bleed. They are associated with obesity, alcohol and hepatic steatosis. (3) HCAs with β-catenin mutations are associated with male hormone administration and glycogen storage disease, frequently undergo malignant transformation and may simulate hepatocellular carcinoma on imaging. (4) The final type is unclassified HCAs. Each of these except the unclassified subtype has a few distinct imaging features, often enabling reasonably accurate diagnosis. Biopsy with immunohistochemical analysis is helpful in difficult cases and has strong implications for patient management.

TEACHING POINTS

• FNHs are benign polyclonal neoplasms with no risk of haemorrhage or malignancy. • HCAs are benign monoclonal neoplasms classified into four subtypes based on immunohistochemistry. • Inflammatory HCAs show an atoll sign with a risk of bleeding and malignant transformation. • HNF-1α HCAs are steatotic HCAs with minimal complications and the best prognosis. • β-Catenin HCA shows variable MRI features and a high risk of malignancy.