Angiomyolipoma of the liver: analysis of typical features and pitfalls based on own experience and literature

Clinical and Contrast-enhanced Ultrasound Characteristics of Epithelioid and Classic Hepatic Angiomyolipoma: Comparison With Alpha-fetoprotein-negative Hepatocellular Carcinoma

Hepatic angiomyolipoma (HAML) comprises epithelioid angiomyolipoma (EAML) and classic hepatic angiomyolipoma (CAML). The imaging appearance of HAML varies widely, and EAML is more easily misdiagnosed as hepatocellular carcinoma (HCC) than as CAML. The clinical and contrast-enhanced ultrasound (CEUS) features of CAML, EAML and HCC with negative alpha-fetoprotein protein expression (HCC[AFP-]) were retrospectively reviewed. The hyper-vascular type was more commonly found in CAML and EAML lesions than in HCC lesions. Most lesions were hyper-enhanced in the arterial phase. CAMLs showed prolonged hyper-enhancement or iso-enhancement during the portal and late phases on CEUS, making them easily distinguishable from HCC(AFP-). Some EAML lesions (41.7%) were hypo-echoic, similar to HCC(AFP-). However, the hypo-enhancement of EAML lesions occurred later than that of HCC(AFP-) lesions. Thus, our findings may be useful in distinguishing among these lesions to improve diagnostic accuracy.

State-of-the-art MR Imaging of Fat-containing Focal Lesions of the Liver

BACKGROUND

Fat can be identified in numerous liver lesions, and usually is not a specific finding. Distinguishing between different kinds of fatty deposits is an important part of differential diagnosis. Magnetic Resonance Imaging (MRI) is superior to other imaging techniques because it allows distinguishing intracellular from macroscopic fat.

DISCUSSION

Intracellular lipid may be found in focal hepatic steatosis, hepatic adenoma, hepatocellular carcinoma and, less commonly, in focal nodular hyperplasia as well as regenerative and dysplastic nodules. Macroscopic fat is seen in angiomyolipoma, lipoma, metastases from fatcontaining neoplasms, primary or metastatic liposarcoma, hydatid cyst, pseudolipoma of the Glisson capsule, pericaval fat collection, lipopeliosis, hepatic teratoma, focal hepatic extramedullary haematopoiesis and adrenal rest tumour.

CONCLUSION

Liver nodules should be characterised with regard to underlying liver condition, MRI characteristics and contrast enhancement pattern, including hepatobiliary phase. In many cases, identification of fatty content may help narrowing the differential diagnosis.

Fat-Containing Liver Lesions on Imaging: Detection and Differential Diagnosis

OBJECTIVE

The purpose of this article is to review how fat is detected on imaging and to discuss the differential diagnosis of fat-containing liver lesions.

CONCLUSION

Fat is a highly useful feature in characterizing liver lesions on imaging. Although a variety of liver lesions can show fat on cross-sectional imaging, the presence of fat usually indicates that the lesion is of hepatocellular origin. Less commonly, nonhepatocellular fatty lesions may be distinguished by ancillary clinical and imaging features.

Comparison of CT and contrast-enhanced ultrasound findings in hepatic angiomyolipoma with pathological correlations

OBJECTIVE

To compare imaging findings of CT and contrast-enhanced US (CEUS) in hepatic angiomyolipoma (HAML) and investigate their pathological correlations.

METHODS

Imaging findings and preoperative diagnosis of CT and CEUS were retrospectively compared head to head in 46 patients with 54 histologically proven HAMLs. Correlations between imaging features and preoperative diagnosis with pathological types of HAMLs were analyzed.

RESULTS

Fat was detected in 100% of lipomatous type, 84.6% of mixed type, and 7.1% of myomatous type (p = 0.000) of HAML at unenhanced CT. Well-defined hyper-echogenicity was displayed in 100% of lipomatous type, 88.5% of mixed type, 50% of myomatous type, and 66.7% of angiomatous type of HAMLs at unenhanced US. More arterial hyper-enhancement was noted on CEUS (100%) than on CT (73.1%) in mixed type (p = 0.015) and in lipomatous type (90.9% vs. 9.1%, p = 0.000) of HAMLs. Washout was present in more HAMLs on CT than on CEUS (42.6% vs. 18.5%, p = 0.007). Correct preoperative diagnosis was suggested in more HAMLs of myomatous type on CEUS than on CT (42.9% vs. 0%, p = 0.016) but showed no difference in other types of HAMLs.

CONCLUSION

There are considerable discrepancies between CT and CEUS findings of HAMLs, and the imaging appearance and preoperative diagnosis of HAMLs on CT and CEUS are significantly affected by pathological types of HAMLs.

Hepatic multiple perivascular epithelioid cell neoplasm: A case report and literature review

Perivascular epithelioid cell neoplasm (PEComa) is a rare tumor type and primary hepatic multiple perivascular is rarer still. The present case report investigated the case of a 40-year-old woman who was admitted to The Second Xiangya Hospital for hepatic multiple tumor by physical examination without any history of abdominal pain or body weight loss. Abdominal plain computed tomography revealed three lesions in the liver. All lesions exhibited a well-defined boarder and only one mass contained fatty tissue in S6 of the liver. An enhanced scan revealed that all lesions were heterogeneous, and were enhanced on the artery phase and on portal vein phase. On delay phase, the lesions revealed continued enhancement, which is isoattenuating to the normal hepatic parenchyma. Following excision of the three masses, the patient was pathologically diagnosed with hepatic multiple PEComa. Short-term re-examination revealed no recurrence.

Differentiation of lipid poor angiomyolipoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging

PURPOSE

To investigate magnetic resonance (MR) findings of angiomyolipoma (AML) on gadoxetic acid-enhanced MR imaging, and to identify features that differentiate AML from hepatocellular carcinoma (HCC) in patients with a low risk of HCC development.

METHODS

This retrospective study was institutional review board approved, and the requirement for informed consent was waived. Twelve patients with hepatic AML who underwent gadoxetic acid-enhanced MRI with no risk factors for HCC development were recruited. Twenty-seven patients with HCC under the same inclusion criteria were recruited as control. Two radiologists analyzed the images in consensus for morphologic features, enhancement patterns, and hepatobiliary phase (HBP) findings. All results were analyzed using the Mann-Whitney test, two-tailed Fisher exact test, and chi-square test.

RESULTS

Patients with AML were younger than those with HCC (48.8 ± 15 years for AML vs. 62.7 ± 14.2 years for HCC, p = 0.008) with female predominance, while most HCC patients were male (75% (9/12) vs. 15% (4/27), p < 0.001). The most prevalent enhancement pattern was arterial enhancement followed by hypointensity at portal or transitional phases for both AMLs (58% (7/12)) and HCCs (74% (20/27)) (p = 0.455). However, during the HBP, AMLs frequently showed more homogeneous hypointensity than HCCs (83% (10/12) vs. 41% (11/27), p = 0.018). When compared with the signal intensity of the spleen, the mean relative signal intensity of the AML was 91.2 ± 15.4%, while in HCCs, it was 128.7 ± 40% (p < 0.001).

CONCLUSIONS

Although AMLs showed similar enhancement patterns to HCCs during the dynamic phases of gadoxetic acid-enhanced MRI, using characteristic MR features of AML during the HBP and demographic differences, one can better differentiate AML from HCC.

MR characterization of focal liver lesions: pearls and pitfalls

Magnetic resonance (MR) can characterize specific tissue subtypes, thus facilitating focal liver lesion diagnosis. Focal liver lesions that are isointense to hyperintense to liver on T1-weighted images are usually hepatocellular in origin. Chemical shift imaging can narrow the differential diagnosis by detecting the presence of lipid or iron. T2 and heavily T2-weigthed fast spin echo imaging can differentiate solid from nonsolid focal liver lesions. The authors illustrate these MR imaging pearls and the uncommon exceptions (pitfalls). The authors hope that you will find this less traditional contribution to the Magnetic Resonance Clinics of North America helpful in clinical practice.

Comparison of MRI features for the differentiation of hepatic angiomyolipoma from fat-containing hepatocellular carcinoma

OBJECTIVE

The purpose of this study was to evaluate MRI features for the differentiation of hepatic angiomyolipoma (HAML) from fat-containing hepatocellular carcinoma.

METHODS

We retrospectively reviewed the MRI findings of 20 patients with 22 hepatic angiomyolipomas and 25 patients with fat-containing hepatocellular carcinomas before surgery. The MRI features and apparent diffusion coefficient (ADC) for the two types of tumors were compared and analyzed.

RESULTS

Fat was not detected in nine (40.9%) of the angiomyolipomas. An enhancement pattern of the washout area was seen in eight (36.4%) of the angiomyolipomas and 21 of the hepatocellular carcinomas (84%) (p = 0.001). The sensitivity, specificity, and accuracy of the enhancement pattern for HAML were 63.6% (14/22), 84% (21/25), and 74.5% (35/47), respectively. An early draining vein was seen in 16 (72.7%) angiomyolipomas and two hepatocellular carcinomas (8%) (p < 0.001). The sensitivity, specificity, and accuracy of an early draining vein for detecting HAML was 72.7% (16/22), 92% (23/25), and 83.0% (39/47), respectively. Tumor vessels were noted in 18 (81.8%) angiomyolipomas and six hepatocellular carcinomas (24%) (p < 0.001). The sensitivity, specificity, and accuracy of tumor vessels for HAML were 81.8% (18/22), 76% (19/25), and 78.7% (37/47), respectively. Pseudocapsules were absent in 21 (95.5%) angiomyolipomas as compared with 3 (12%) hepatocellular carcinomas (p < 0.001). The sensitivity, specificity, and accuracy of pseudocapsules for HAML were 95.5% (21/22), 88% (22/25), and 91.5% (43/47), respectively. The ADC of the angiomyolipomas (1.92 ± 0.29 × 10(-3 )mm(2)/s) was significantly higher than that for hepatocellular carcinomas (1.33 ± 0.25 × 10(-3 )mm(2)/s) (p < 0.001).

CONCLUSION

The presence of an early draining vein and tumor vessels, the absence of pseudocapsules and a higher ADC in the hypervascular hepatic tumor on the MRI were helpful for the differentiation of hepatic angiomyolipoma from fat-containing hepatocellular carcinoma.

Diagnosis and treatment of hepatic angioleiomyolipoma: A case report and literature review

AIM: To investigate the clinical features, imaging manifestations, pathological characteristics, differential diagnosis, treatment and prognosis of hepatic angiomyolipoma (HAML).

METHODS: A case of HAML diagnosed at our hospital is reported. A review of the literature was performed to retrospectively analyze 540 cases reported in China between 1987 and 2014.

RESULTS: HAML was more frequently found in females (2.7:1). Most of the patients (66.7%) presented no significant symptoms, and tumor marks were negative in all the patients. CT performed better for preoperative diagnosis than MRI (CT vs MRI: χ² = 11.321, P = 0.001) and ultrasound. Immunohistochemical analyses revealed that the positive expression rates of human melanoma black-45 antigen (HMB-45), smooth muscle actin (SMA), Vimentin, CD34 and CD117 in HAML were 97.8% (357/365), 93.7% (207/221), 62.5% (30/48), 40.5% (51/126) and 39.0% (48/123), respectively. The expression of HMB-45 was considered to have great significance in confirming the diagnosis. Of all the patients, 521 (96.3%) underwent surgical intervention, and recurrence or metastasis was found in only 3 patients during follow-up.

CONCLUSION: HAML lacks specific symptoms or signs, has diverse imaging manifestations, and can be easily misdiagnosed. Pathological and immunohistochemical analyses are essential for diagnosis, and surgical treatment has a good prognosis.

Myomatous hepatic angiomyolipoma: imaging findings in 14 cases with radiological-pathological correlation and review of the literature

OBJECTIVE

To display and analyse the imaging features of myomatous hepatic angiomyolipomas (MHAMLs).

METHODS

The imaging features (CT = 9; MRI = 10; ultrasound = 10; contrast-enhanced ultrasound = 4) of 14 patients with pathologically proven MHAMLs were reviewed retrospectively.

RESULTS

MHAMLs were surgically resected in the 14 patients (10 females and 4 males; age, 27-64 years; mean, 45 years), all of whom had negative hepatitis markers and were positive for the immunohistochemical stain homatropine methylbromide-45. The tumours were solitary and well defined, and ranged in size from 1.9 to 9.1 cm (mean, 5.7 cm). On dynamic contrast-enhanced CT, MRI and ultrasound scans, all tumours showed fast strong enhancement in the arterial phase and moderate washout in the portal venous and delayed phases, and the greater portions of the tumours were slightly lower than the surrounding hepatic parenchyma. In some cases, a small area of prolonged or increasing enhancement in the tumour was recognized in the delayed phase. Early draining vessels to the portal vein or hepatic vein could be seen in some cases. However, no capsular signs could be confidently identified in the delayed phase. Haemorrhagic cavities were recognized in two cases, and nodular low-intensity areas in the tumours on T2 weighted imaging that showed slow and faint enhancement on dynamic scans were seen in two cases. However, no necrosis was identified.

CONCLUSION

Dynamic enhanced imaging studies revealed some specific features of MHAMLs that distinguish them from other hypervascular hepatic tumours, especially when combined with clinical features. Familiarity with imaging and clinical features of MHAMLs could avoid unnecessary surgical resection of these generally benign tumours.

ADVANCES IN KNOWLEDGE

This article systematically describes the imaging features of MHAMLs.