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

Fat-Poor Hepatic Angiomyolipoma in Noncirrhotic Livers: Imaging Features, Pathology, and Differential Diagnosis

OBJECTIVE

To investigate imaging features of fat-poor hepatic angiomyolipomas in noncirrhotic livers in order to enhance the diagnostic accuracy for this condition.

METHODS

The clinical and imaging data of 19 patients with fat-poor hepatic angiomyolipoma (fpHAML) was retrospectively analyzed.

RESULTS

Of the 19 patients without hepatitis, cirrhosis, or sarcoidosis, 16 had no clinical symptoms. There were 20 lesions in 19 patients. Macroscopic fat, calcification, hemorrhage, necrosis, and pseudocapsule were not observed in the 20 lesions. All lesions showed marked enhancement on the arterial phase, and the degree of enhancement was significantly higher than that in the adjacent hepatic parenchyma. In 8 cases, the enhancement of the portal phase was higher than that in the arterial phase. Multiple intratumor vessels were observed in the tumor, and lesions with diameters larger than 3.0 cm were more frequently observed. The degree of enhancement of 18 lesions on portal phase or delayed phase was slightly higher than or equal to that in the surrounding hepatic parenchyma. The lesions were hyperintense on diffusion-weighted imaging and showed homogeneous hypointensity on the hepatobiliary phase. Only 6 cases showed the presence of an early draining vein.

CONCLUSIONS

These imaging features have some implications for the diagnosis of fpHAML. Therefore, an increased awareness of fpHAML is needed among radiologists.

TSC2 inactivation, low mutation burden and high macrophage infiltration characterise hepatic angiomyolipomas

AIMS

Although TSC1 or TSC2 inactivating mutations that lead to mTORC1 hyperactivation have been reported in hepatic angiomyolipomas (hAML), the role of other somatic genetic events that may contribute to hAML development is unknown. There are also limited data regarding the tumour microenvironment (TME) of hAML. The aim of the present study was to identify other somatic events in genomic level and changes in TME that contribute to tumorigenesis in hAML.

METHODS AND RESULTS

In this study, we performed exome sequencing in nine sporadic hAML tumours and deep-coverage targeted sequencing for TSC2 in three additional hAML. Immunohistochemistry and multiplex immunofluorescence were carried out for 15 proteins to characterise the tumour microenvironment and assess immune cell infiltration. Inactivating somatic variants in TSC2 were identified in 10 of 12 (83%) cases, with a median allele frequency of 13.6%. Five to 18 somatic variants (median number: nine, median allele frequency 21%) not in TSC1 or TSC2 were also identified, mostly of uncertain clinical significance. Copy number changes were rare, but detection was impaired by low tumour purity. Immunohistochemistry demonstrated numerous CD68+ macrophages of distinct appearance from Küpffer cells. Multiplex immunofluorescence revealed low numbers of exhausted PD-1+/PD-L1+, FOXP3+ and CD8+ T cells.

CONCLUSION

hAML tumours have consistent inactivating mutations in TSC2 and have a low somatic mutation rate, similar to other TSC-associated tumours. Careful histological review, standard IHC and multiplex immunofluorescence demonstrated marked infiltration by non-neoplastic inflammatory cells, mostly macrophages.

Benign focal liver lesions: The role of magnetic resonance imaging

Liver lesions are common findings in radiologists' daily routine. They are a complex category of pathology that range from solitary benign lesions to primary liver cancer and liver metastases. Benign focal liver lesions can arise from different liver cell types: Epithelial (hepatocytes and biliary cells) and nonepithelial (mesenchymal cells). Liver magnetic resonance imaging (MRI) is a fundamental radiological method in these patients as it allows with its multiparametric approach optimal non-invasive tissue characterization. Furthermore, advanced liver MRI techniques such as diffusion-weighted imaging and hepatobiliary contrast agents have improved the detection of focal liver lesions and can be highly effective in differentiating pseudotumor from tumors, as well as benign from malignant lesions, and can also be used for differential diagnosis. Although histological examination can be useful in making a definitive diagnosis, MRI is an important modality in the diagnosis of liver lesions with a significant impact on patient care. This aim of this review is to provide a comprehensive overview of benign liver lesions on MRI.

Comparison of MRI Features of Epithelioid Hepatic Angiomyolipoma and Hepatocellular Carcinoma: Imaging Data From Two Centers

Introduction: Epithelioid hepatic angiomyolipoma (Epi-HAML) can easily be misdiagnosed as a malignant tumor such as hepatocellular carcinoma (HCC) because of the low-fat content on imaging. We analyzed and compared the magnetic resonance imaging (MRI) features of Epi-HAML and HCC, which would aid in disease diagnosis.

Methods: We included 30 pathologically confirmed patients with Epi-HAML and 80 with HCC, who underwent both MRI unenhanced scan and three-phase contrast-enhanced MRI scan. The clinical and MRI features of the two groups were summarized and analyzed.

Results: Epi-HAML showed significant differences compared to HCC group in terms of clinical features such as sex preference, age, concomitant diseases (hepatitis B and cirrhosis), and elevated plasma alpha-fetoprotein (AFP) (P < 0.001). In addition, there were statistically significant differences between both tumor types with regard to conventional MRI findings such as a solitary tumor (100 vs. 83.8%, P = 0.018), well-defined (93.3 vs. 71.3%, P = 0.027), mild hyperintensity (40.0 vs. 3.7%, P < 0.001) on DWI with high b-value, fat within the tumor (43.3 vs. 8.8%, P < 0.001), and rare necrosis (3.3 vs. 26.3%, P = 0.016). Besides, Epi-HAML displayed significant differences compared to HCC in terms of contrast-enhanced MRI characteristics such as draining hepatic vein (30.0 vs. 3.8%, P < 0.001), portal vein tumor thrombus (0 vs. 13.8%, P = 0.033), hypointensity at delayed phase (70.0 vs. 95%, P = 0.001), intra-tumor vessel at delayed phase (36.7 vs. 10.0%, P = 0.003), pseudocapsule (20.0 vs. 78.8%, P < 0.001), and prolonged enhancement (56.7 vs. 1.2%, P < 0.001).

Conclusion: Epi-HAML frequently occurs in middle-aged women and usually lacks characteristic clinical symptoms. Typically, Epi-HAML presents as an isolated and well-defined tumor with rich vasculature. Specific MRI features such as intra-tumor fat, intra-tumor vessel, draining hepatic vein, prolonged enhancement, and lack of capsule may contribute to a more confident diagnosis of Epi-HAML.

Primary benign liver lesions

Benign focal liver lesions can origin from all kind of liver cells: hepatocytes, mesenchymal and cholangiocellular line. Their features at imaging may sometimes pose difficulties in differential diagnosis with malignant primary and secondary lesions. In particular, the use of MDCT and MRI with extracellular and hepatobiliary Contrast Agents may non invasively help in correct interpretation and definition of hepatocellular or mesenchymal and inflammatory nature, allowing to choose the best treatment option. The peculiarities of main benign liver lesions at US, CT and MRI are described, with special attention to differential diagnosis and diagnostic clues.