Fat-containing lesions of the liver : A pictorial essay

Fat in mass in primary liver lesions: are usual MRI diagnostic criteria of both malignant and benign liver lesions still applicable?

PURPOSE

To evaluate the accuracy of the usual MRI diagnostic patterns of primary liver lesions applied to the diagnosis of pathologically proven fat-containing liver lesions.

MATERIALS AND METHODS

This monocentric IRB approved retrospective study included all patients with pathologically proven focal liver lesions and documented intra-tumoral fat on pathology and who underwent preoperative liver MRI for characterization. Both liver morphology and usual lesion MRI features were analyzed and their distribution correlated to the final pathological result (Khi-2 or Fisher exact tests, Student t-test or Mann-Whitney U test, as appropriate). The Sensitivity (Se) and Specificity (Sp) of MRI patterns known to be associated to both Hepatocellular Carcinoma (HCC), Focal Nodular Hyperplasia (FNH), and Hepatocellular Adenoma (HCA) subtypes were evaluated.

RESULTS

Between March 2014 and November 2021, 66 lesions were included, corresponding to: 26 HCC, 32 HCA, 6 FNH and 2 hepatic angiomyolipoma (HAML). All lesions developed on a dysmorphic liver were HCC. A non-rim arterial phase hyperenhancement with a washout and an enhancing capsule had a 98% specificity for HCC diagnosis; A homogeneous dropout of signal on the opposed phase had a sensitivity of 92% and a specificity of 89% for the diagnosis of HNF1alpha inactivated subtype of HCA (HHCA). The FNH pattern was specific at 100% for the diagnosis of FNH with a 40% Se. Finally, the accuracy of inflammatory hepatocellular adenoma (IHCA) pattern had a low 60% Se but a high 89% Sp for IHCA diagnosis.

CONCLUSION

Known MRI patterns remain reliable for the accurate diagnosis of primary liver tumors on MRI even in fat-containing lesions.

Hepatocellular Carcinoma with Macroscopic Fat Metamorphosis: A Case Series

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related deaths in the world, with hepatitis B and C as its main causes. HCC can have fat metamorphosis which leads to a better prognosis, though this is more commonly found in lesions smaller than 3 cm in diameter, and usually contains intravoxel fat. In this case series, we present three cases of HCC with macroscopic fat metamorphosis as examined using CT scan and MRI. Macroscopic fat is seen using CT as a hypodense mass with attenuation of −10 to −100 HU, or MRI using fat-saturation technique. Intravoxel fat can be seen on MRI using fat saturation chemical shift technique, appearing as signal loss during opposed phase and increased signal during in-phase. The differential diagnoses of HCC with fat metamorphosis are angiomyolipoma, hepatic adenoma, nodular steatosis, focal nodular hyperplasia, dysplastic nodule, liposarcoma, and hepatic metastasis. Enhancement patterns of the fat and non-fat component; intra-tumoral fat distribution; the presence of cirrhosis; the presence of atoll sign; and history of viral hepatitis are useful clues for differentiation of HCC with other differential diagnoses.

Hepatic epithelioid angiomyolipoma: contribution of a new case

In relation to the article published by Ortiz S et al. (1), we have recently seen a 37-year-old female who presented to the Emergency Department with pain in right hypochondrium and a mild increase in transaminase levels. An ultrasound was performed that showed a large 13-cm tumor in the right hepatic lobe, which was heterogeneous with hyperechogenic and anechoic areas.

The Histopathological Features and CT/MRI Imaging Performances in Hepatic Angiomyolipoma Patients

AIM

To evaluate the diagnostic value of dynamic contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) in the differential diagnosis of hepatic angiomyolipoma (HAML) and hepatocellular carcinoma (HCC) and to clarify the relationship between histopathological features and CT or MRI imaging performances in HAML.

MATERIAL AND METHODS

Six HAML and 33 non-cirrhotic HCC patients confirmed by histopathology were retrospectively analyzed. The serum biomarkers, CT and MRI examinations were conventionally performed before the confirmatory histological diagnosis. The clinical data from their medical records was also analyzed.

RESULTS

Six HAML patients were annotated as two types according to CT and MRI imaging characteristics, including hypovascular type (n = 1) and hypervascular type (n = 5). The imaging performances of the 33 HCC patients were hypervascular type. Moreover, all the 5 hypervascular type HAML patients were misdiagnosed as HCC by CT or MRI. We also found that the hypervascular type of HAML patients contained more vessels and less fatty tissues in histopathology than hypovascular type of HAML patients. However, the clinical features included HCC high risk factors (hepatitis B or C), non-specific symptoms, male and increased serum alpha fetoprotein (AFP) were more common in HCC patients than HAML patients (P < 0.05, respectively).

CONCLUSIONS

The CT or MRI imaging performances of HAML patients containing more vessels and less fatty tissues in histopathology resemble the imaging performance of HCC patients. These clinical features may be of great help in the differential diagnosis in the current clinical practices.

MDCT features of hepatocellular carcinoma (HCC) in non-cirrhotic liver

PURPOSE

To describe the multidetector row computed tomography (MDCT) imaging features of HCC that develops in patients who are free from underlying liver cirrhosis and to determine if the MDCT presentation of this specific tumor differs from that of the more common HCC that develops in patients with liver cirrhosis using a retrospective case-control study.

PATIENTS AND METHODS

The MDCT examinations of 38 patients with HCC in non-cirrhotic liver (group 1) were quantitatively and qualitatively analyzed and compared to those obtained in 38 patients with HCC in cirrhotic liver (group 2) matched for age and gender. Quantitative and qualitative characteristics of HCC of both groups were compared using univariate analysis.

RESULTS

HCCs were significantly larger in group 1 (81.5mm±55.5) than in group 2 (44.5mm±39.1 SD; P=0.0015). In group 1, HCCs were more frequently single tumors (87%) than in group 2 (37%) (P<0.0001), encapsulated (92% vs. 47% respectively; P<0.0001), had more frequently fatty component (24% vs. 8%, respectively; P=0.0279) and internal hemorrhage (29% vs. 3%, respectively; P=0.0033). No significant differences were found between the two groups for location, hyperenhancement of HCC during the arterial phase, washout during the portal phase, endoluminal portal involvement by HCC, endoportal cruoric thrombus, invasion of adjacent organs and underlying liver steatosis.

CONCLUSION

HCC in non-cirrhotic liver are larger than those observed in cirrhotic liver and more frequently present as a single encapsulated tumor. They have the same patterns of enhancement than HCC that develops in cirrhotic liver.