Magnetic resonance of focal liver lesions in hepatic cirrhosis and chronic hepatitis

How to Differentiate Borderline Hepatic Nodules in Hepatocarcinogenesis: Emphasis on Imaging Diagnosis

BACKGROUND

Rapid advances in liver imaging have improved the evaluation of hepatocarcinogenesis and early diagnosis and treatment of hepatocellular carcinoma (HCC). In this situation, detection of early-stage HCC in its development is important for the improvement of patient survival and optimal treatment strategies. Because early HCCs are considered precursors of progressed HCC, precise differentiation between a dysplastic nodule (DN), especially a high-grade DN, and early HCC is important. In clinical practice, these nodules are frequently called "borderline hepatic nodules."

SUMMARY

This article discusses radiological and pathological characteristics of these borderline hepatic nodules and offers an understanding of multistep hepatocarcinogenesis by focusing on the descriptions of the imaging changes in the progression of DN and early HCC. Detection and accurate diagnosis of borderline hepatic nodules are still a challenge with contrast enhanced ultrasonography, CT, and MRI with extracellular contrast agents. However, gadoxetic acid-enhanced MRI may be useful for improving the diagnosis of these borderline nodules.

KEY MESSAGES

Since there is a net effect of incomplete neoangiogenesis and decreased portal venous flow in the early stage of hepatocarcinogenesis, borderline hepatic nodules commonly show iso- or hypovascularity. Therefore, precise differentiation of these nodules remains a challenging issue. In MRI using hepatobiliary contrast agents, signal intensity of HCCs on hepatobiliary phase (HBP) is regarded as a potential imaging biomarker. Borderline hepatic nodules are seen as nonhypervascular and hypointense nodules on the HBP, which is important for predicting tumor behavior and determining appropriate therapeutic strategies.

Hypovascular hypointense nodules on hepatobiliary phase without T2 hyperintensity on gadoxetic acid-enhanced MR images in patients with chronic liver disease: long-term outcomes and risk factors for hypervascular transformation

PURPOSE

To evaluate the long-term outcomes and imaging features associated with hypervascularization of hypovascular nodules that show T2 iso-/hypointensity and hypointensity on hepatobiliary phase (HBP) of gadoxetic acid-enhanced magnetic resonance (MR) images in patients with chronic liver disease.

MATERIALS AND METHODS

Sixty patients and 114 nodules, which were hypovascular and iso-/hypointense on T2-weighted images and hypointense on HBP of gadoxetic acid-enhanced MRI, were included. We evaluated the effect of baseline clinical features, baseline MR features and growth rate on subsequent hypervascularization.

RESULTS

Twenty-seven nodules in 21 patients transformed to hypervascular hepatocellular carcinoma (HCC). Using multivariate Cox analysis, T1 hyperintensity (hazard ratio [HR] = 2.69, P = 0.021), previous history of HCC (HR = 2.64, P = 0.021), and initial nodule size (HR = 1.09, P = 0.046) were identified to be associated with hypervascularization. The growth rate of nodules was a more powerful determinant of subsequent hypervascularization than baseline clinical and MR features. At long-term follow-up after >3 years, only one nodule with T1 isointensity showed hypervascularization.

CONCLUSION

Careful follow-up or diagnostic procedures, such as biopsy, should be considered for up to 3 years after detection of hypointense nodules on HBP with T1 hyperintensity or a higher growth rate.

KEY POINTS

• T1 hyperintensity is a baseline MR predictive factor for subsequent hypervascularization. • A higher growth rate is a more powerful determinant of subsequent hypervascularization. • Management of patients with these predictive factors requires more attention.

CT and MR imaging diagnosis and staging of hepatocellular carcinoma: part I. Development, growth, and spread: key pathologic and imaging aspects

Computed tomography (CT) and magnetic resonance (MR) imaging play critical roles in the diagnosis and staging of hepatocellular carcinoma (HCC). The first article of this two-part review discusses key concepts of HCC development, growth, and spread, emphasizing those features with imaging correlates and hence most relevant to radiologists; state-of-the-art CT and MR imaging technique with extracellular and hepatobiliary contrast agents; and the imaging appearance of precursor nodules that eventually may transform into overt HCC.

Hepatocarcinogenesis: imaging-pathologic correlation

Rapid advances in liver surgery, including liver transplantation, radiology, and pathology, have created a need for clinically relevant nomenclature for premalignant and early lesions of hepatocellular carcinoma (HCC). Precancerous lesions include dysplastic foci and dysplastic nodules (DNs) characterized by cytologic or structural atypia. Although imaging diagnosis is playing a crucial role in the evaluation of hepatocarcinogenesis and early diagnosis of HCC, it is still challenging to accurately characterize borderline nodules such as small arterially enhancing lesions or hypovascular nodules. This article discusses pathological and radiological features of these small nodular lesions and offers insights into the multistep process of hepatocarcinogenesis by describing the progression of pathologic change linking DNs to HCC.

The effect of gadoxetic acid enhancement on lesion detection and characterisation using T₂ weighted imaging and diffusion weighted imaging of the liver

OBJECTIVES

To evaluate the effect of gadoxetic acid enhancement on the detection and characterisation of focal hepatic lesions on T(2) weighted and diffusion weighted (DW) images.

METHODS

A total of 63 consecutive patients underwent T(2) weighted and DW imaging before and after gadoxetic acid enhancement. Two blinded readers independently identified all of the focal lesions using a five-point confidence scale and characterised each lesion using a three-point scale: 1, non-solid; 2, indeterminate; and 3, solid. For both T(2) weighted and DW imaging, the accuracies for detecting focal lesions were compared using the free-response receiver operating characteristic analysis; the accuracies for lesion characterisation were compared using the McNemar test between non-enhanced and gadoxetic acid-enhanced image sets. For hepatic lesions ≥ 1 cm, the lesion-to-liver contrast-to-noise ratio (CNR) and the apparent diffusion coefficient (ADC) were compared in the non-enhanced and enhanced image sets using the generalised estimating equations.

RESULTS

For both T(2) weighted and DW images, the accuracies for detecting focal lesions (p ≥ 0.52) and those for lesion characterisation (p ≥ 0.63) did not differ significantly between the non-enhanced and enhanced image sets. The lesion-to-liver CNR was significantly higher on enhanced DW images than on non-enhanced DW images (p=0.02), although the difference was not significant for T(2) weighted imaging (p=0.65). The mean ADC values of lesions did not differ significantly on enhanced and non-enhanced DW imaging (p=0.75).

CONCLUSION

The acquisition of T(2) weighted and DW images after administration of gadoxetic acid has no significant effect on the detection or characterisation of focal hepatic lesions, although it improves the lesion-to-liver CNR on DW images.

Surveillance for hepatocellular carcinoma and early diagnosis

Good management of patients at risk for the development of hepatocellular carcinoma includes regular ultrasound surveillance, and aggressive management of lesions detected at ultrasound. Good radiology and good pathology are essential to the appropriate management of these small lesions. With good quality testing it is possible to cure the majority of HCCs using minimally invasive techniques such as radiofrequency ablation. Such an approach has the potential to convert HCC from a disease in which incidence more or less equaled mortality to one in which cure is frequently possible.

Hepatocellular dysplastic nodules

The multistep process of hepatic carcinogenesis is mirrored by the morphologic classification of lesions detectable in cirrhosis, which include large regenerative nodules (LRN), low grade dysplastic nodules (LGDN), and high grade dysplastic nodules (HGDN). The latter belong to the "bordeline malignancy" category requiring accurate distinction from well-differentiated and early hepatocellular carcinoma (HCC). Nodules in cirrhosis are usually detected by non-invasive imaging techniques, which are unable to discriminate malignant from non-malignant forms, particularly in the 1-2-cm sized group. Liver biopsy is essential in providing practical diagnostic information to hepathologists in the management of cirrhotic patients with ultrasound (US)-detectable nodules. Histologic diagnosis on liver samples is based on the accurate search of a set of cyto-architectural features (e.g. cell atypia, cell crowding, trabecular thickness, microacini) and by a supplement of histochemical (Gomori staining) and immunocytochemical stainings. The latter rely upon the search of both well established and novel markers, targeted to evaluate stromal invasion (CK7/19), the vascular pattern (ASMA and CD34), or tumor markers (including HSP70 and glipican-3). Still, the diagnostic sensitivity is limited by the type and size of sampling and by its representativity of the entire lesion. Thus, the best diagnostic approach requires the integration ofclinical, morphological, and immunocytochemical information with imaging data (i.e. US pattern, perfusional pattern, helical computed tomography/magnetic resonance pattern). Molecular data are still under evaluation as to their diagnostic efficacy in this controversial field. Discrepancies have emerged recently between Eastern and Western interpretation of these lesions, particularly in the category of "borderline" nodules that are mostly labelled as early, well differentiated HCC by Eastern pathologists and as HGDN by Western pathologsts. Novel and more objective phenotypical and molecular markers are needed to discriminate within the grey area of borderline lesions that, epidemiologically, are likely distinct between Eastern and Western geographic areas. These tools might allow a better understanding of the boundaries of the process going from high grade dysplasia to in situ HCC and from the latter to microinvasive HCC and advanced HCC, for proper clinical management and optimal therapy.

Improving the prediction of hepatocellular carcinoma in cirrhotic patients with an arterially-enhancing liver mass

In the United States, cirrhotic patients with known or suspected hepatocellular carcinoma (HCC) are prioritized for liver transplantation. Noninvasive criteria for the diagnosis of HCC rely on arterial enhancement of a mass. The aim of this study was to determine whether clinical, laboratory, and / or radiologic data can improve the prediction of HCC in cirrhotic patients with an arterially-enhancing mass. Between May 2002 and June 2003, dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of consecutive patients with liver cirrhosis and a solid mass were reviewed by 2 radiologists blinded to the clinical diagnosis. Clinical, laboratory, and radiologic data were recorded for all patients. A total of 94 patients with cirrhosis and an arterially-enhancing liver mass were studied, 66 (70%) of whom had HCC. Alpha-fetoprotein (AFP) >20 ng/mL (P = .029), tumor size >2 cm (P = .0018), and delayed hypointensity (P = .0001) were independent predictors of HCC. Delayed hypointensity of an arterially-enhancing mass had a sensitivity of 89% and a specificity of 96% for HCC. The presence of delayed hypointensity was the only independent predictor of HCC among patients with arterially-enhancing lesions <2 cm (odds ratio, 6.3; 95% confidence interval [CI], 1.8-13), with a sensitivity of 80% and a specificity of 95%. In conclusion, delayed hypointensity of an arterially-enhancing mass was the strongest independent predictor of HCC, regardless of the size of the lesion. If additional studies confirm our results, the noninvasive criteria utilized to make a diagnosis of HCC should be revised.

Screening for hepatocellular carcinoma

There is currently no evidence that screening patients at risk for hepatocellular carcinoma reduces mortality from the disease. Nonetheless, screening is widely practiced. Screening is a process that includes selecting patients, applying screening tests, deciding on recall policies, and subsequently proving or disproving the presence of cancer. The literature on screening for hepatocellular carcinoma is confusing at best, and does not adequately consider the many biases that result from uncontrolled and retrospective studies. Nonetheless, screening can be justified because it is likely that mortality is decreased by adequate treatment of small cancers, particularly in the era of liver transplantation. False-positive screening test results are common. Once an abnormal screening result is obtained there is little guidance from the literature as to how patients should be investigated further, nor about how to determine whether the screening test result was a false-positive. This should at minimum include short interval follow-up with CT scans and MRI's.

MRI features of regenerative and dysplastic nodules in cirrhotic liver

AIM: To study MR features of the regenerative nodule (RN) and dysplastic nodule (DN) in the cirrhotic liver.

METHODS: MRI was performed in 26 cases of suspected cirrhotic liver with RN and DN. Additional enhanced MRI with administration of Gd-DTPA on T1WI was performed in 18 of 26 cases. Meanwhile in 10 of 18 both Gd-DTPA and SPIO (Feridex) enhancement were underwent one day apart. All patients were confirmed by aspiration biopsy or histopathology. MRI was compared to the pathological findings.

RESULTS: In 26 cases, there were 12 cases of regenerative nodules measuring 0.3-1cm in size, and 14 dysplastic nodules including 8 nodules measuring ≥1 cm and <3 cm in size, and 6 nodules measuring ≥3 cm. Their MR appearances were as followings: nodules with <1 cm in size showed isointensity on T₁WI and hypointensity on T₂WI, of which the intensity was as isointense as the surrounding hepatic parenchyma on enhanced MRI with administration of Gd-DTPA or SPIO. In 8 cases with nodules measuring 1-3 cm in size, 5 cases appeared hyperintense on T1WI and hypointense on T₂WI as well as the enhancement as that of nodules with <1 cm in size; the other 3 cases appeared hypointense on T₁WI and hyperintense on T₂WI, and were enhanced after administration of Gd-DTPA but hyperintense on SPIO enhancing MRI, which indicated malignant transformation of dysplastic nodule into hepatocellular carcinoma (HCC) arising from hepatic nodule on histopathology. In 6 cases of nodules measuring >3 cm in size, 2 cases appeared hyperintense compared to the surrounding hepatic parenchyma on T₁, T₂WI and enhanced MRI, one of which was documented "nodule within a nodule" on T₂WI. The 2 cases were demonstrated well-differentiated HCC. The other 4 cases showed hyperintense on T1WI, and hypointense on T₂WI and enhanced MRI. Sometimes, normal vessels were seen to pass through the surface of macroregenerative nodule. Additionally, RN and DN had the same pattern of the time-signal intensity course as the normal surrounding hepatic parenchyma, but malignant transformation of DN appeared fast wash-in and wash-out.

CONCLUSION: RN of cirrhosis has features on MRI that usually allow distinction from HCC but not always from DN. A helpful distinction between HCC and DN is that the latter is almost never hyperintense on T₂WI. Additionally, the followings indicate malignant transformation of DN when DN appears a ring like enhancement after injection of Gd-DTPA, and fast wash-in and wash-out as well as hyperintensity on SPIO enhanced MRI.

Hepatocellular nodules in cirrhosis: focus on diagnostic criteria on liver biopsy. A Western experience

The spectrum of so-called space-occupying small (0.5-2.5 cm) sizable nodules arising in the cirrhotic liver includes a series of hyperplastic (large regenerative), dysplastic (low- and high-grade dysplastic), and malignant hepatocellular (well-differentiated hepatocellular carcinoma, HCC) nodules. Major progress in their classification and understanding was achieved through image analysis techniques and careful histological dissection of explanted native livers. Needless to say, the actual understanding of their natural history is crucial to a proper histological classification. The differential diagnosis of these hepatocellular nodules is difficult, particularly on biopsy specimens of focal liver lesions revealed by ultrasound (US), taken during the follow-up of cirrhotic patients. In this study we attempted to summarize, on the basis of our experience, essential clinicopathological features useful to distinguish the different nodules on needle biopsy. Synoptic tables of differential diagnosis and figures of elementar lesions, which have to be looked for, are provided. Only the continuous integration of clinical features, image analysis information of pathological findings, and follow-up data allows establishing the autonomy of these polymorphic and controversial entities and the boundaries between them.