Inflammatory myofibroblastic tumours of the liver: Gadoxetic acid-enhanced and diffusion-weighted MRI findings with 18F-FDG PET/CT and clinical significance of regression on follow-up

Impact of velocity- and acceleration-compensated encodings on signal dropout and black-blood state in diffusion-weighted magnetic resonance liver imaging at clinical TEs

PURPOSE

The study aims to develop easy-to-implement concomitant field-compensated gradient waveforms with varying velocity-weighting (M1) and acceleration-weighting (M2) levels and to evaluate their efficacy in correcting signal dropouts and preserving the black-blood state in liver diffusion-weighted imaging. Additionally, we seek to determine an optimal degree of compensation that minimizes signal dropouts while maintaining blood signal suppression.

METHODS

Numerically optimized gradient waveforms were adapted using a novel method that allows for the simultaneous tuning of M1- and M2-weighting by changing only one timing variable. Seven healthy volunteers underwent diffusion-weighted magnetic resonance imaging (DWI) with five diffusion encoding schemes (monopolar, velocity-compensated (M1 = 0), acceleration-compensated (M1 = M2 = 0), 84%-M1-M2-compensated, 67%-M1-M2-compensated) at b-values of 50 and 800 s/mm2 at a constant echo time of 70 ms. Signal dropout correction and apparent diffusion coefficients (ADCs) were quantified using regions of interest in the left and right liver lobe. The blood appearance was evaluated using two five-point Likert scales.

RESULTS

Signal dropout was more pronounced in the left lobe (19%-42% less signal than in the right lobe with monopolar scheme) and best corrected by acceleration-compensation (8%-10% less signal than in the right lobe). The black-blood state was best with monopolar encodings and decreased significantly (p < 0.001) with velocity- and/or acceleration-compensation. The partially M1-M2-compensated encoding schemes could restore the black-blood state again. Strongest ADC bias occurred for monopolar encodings (difference between left/right lobe of 0.41 μm2/ms for monopolar vs. < 0.12 μm2/ms for the other encodings).

CONCLUSION

All of the diffusion encodings used in this study demonstrated suitability for routine DWI application. The results indicate that a perfect value for the level of M1-M2-compensation does not exist. However, among the examined encodings, the 84%-M1-M2-compensated encodings provided a suitable tradeoff.

18F-FDG PET/CT Imaging of G-CSF-Producing Inflammatory Myofibroblastic Tumor of the Pleura

ABSTRACT

We report a case of granulocyte colony-stimulating factor (G-CSF)-producing inflammatory myofibroblastic tumor of the pleura in a 71-year-old man. Contrast-enhanced CT demonstrated multiple pleural masses with pulmonary hilar lymph nodes swelling. 18F-FDG PET/CT demonstrated marked focal FDG uptake in the thoracic masses with diffuse uptake in the bone marrow. Based on the pathological findings and elevated serum G-CSF level, the patient was diagnosed as G-CSF-producing inflammatory myofibroblastic tumor. Because G-CSF-producing tumors demonstrate aggressive clinical course, early and accurate diagnosis is important.

What do we know about inflammatory myofibroblastic tumors? - A systematic review

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) are rare intermediate-grade neoplasms that have a high recurrence rate after excision and exhibit low metastatic potential. These tumors contain proliferating neoplastic, fibroblastic and myofibroblastic cells, and are also characterized by chronic inflammatory infiltration by lymphocytes, plasma cells, eosinophils, and histiocytes. They belong to the group of inflammatory spindle cell lesions. Some reactive lesions, such as inflammatory pseudotumors, may appear to be IMTs, which makes their differential diagnosis extremely difficult. The aim of this article is to compile the recent information on IMTs to aid in their diagnosis and treatment.

METHODS

We reviewed articles published between 2017 and 2021, which were selected from online medical databases. In addition, some earlier articles and latest scientific monographies were analyzed.

RESULTS

The terminology used for inflammatory spindle cell lesions seems to be confusing. The terms "inflammatory myofibroblastic tumors" and "inflammatory pseudotumors" are interchangeably used by many scientists. However, a detailed analysis of the development of terminology suggests that the term "inflammatory myofibroblastic tumors" should be used to refer to a neoplastic lesion.

CONCLUSIONS

IMTs are rare neoplasms, which have not been investigated in detail due to the difficulty in collecting a large number of cases. Thus, our knowledge about this disease remains unsatisfactory. Recently developed techniques such as next-generation sequencing and computer-aided histopathological diagnosis may be useful in understanding the etiopathology of IMTs, which will help in the selection of the most appropriate therapy for patients.

Inflammatory Myofibroblastic Tumor of the Porta Hepatis: A Case Report

A 43-year-old man presented with painless jaundice. Imaging revealed a porta hepatis mass compressing the common bile duct. Endoscopic biopsy was negative for malignancy. Complete surgical resection was performed. Pathological assessment showed IGg4 negative inflammatory myofibroblastic tumor.

Inflammatory Myofibroblastic Tumor of the Liver Mimicking Metastasis on 18F-FDG PET/CT

A 62-year-old woman with history of stage III endometrial cancer was found to have a small enhancing liver lesion on follow-up abdominal CT and MRI, suspicious for metastasis. Subsequent F-FDG PET/CT was performed, demonstrating intense uptake within the liver lesion, consistent with metastasis. Subsequently, laparoscopic wedge liver lesion resection was performed. Histopathologic examination confirmed the diagnosis of inflammatory myofibroblastic tumor (IMT) with predominant inflammatory cells. Although solitary liver IMTs are rare occurrences with imaging features overlapping with malignancy, IMT should be considered in the differential diagnosis of suspicious liver lesions, especially when the pattern of spread is unusual.

Differentiation of Hepatic Sclerosed Hemangiomas From Cavernous Hemangiomas Based on Gadoxetic Acid-Enhanced Magnetic Resonance Imaging Features

OBJECTIVE

The objective of this study was to evaluate the imaging features of a hepatic sclerosed hemangioma by comparing them with those of a cavernous hemangioma using magnetic resonance imaging with gadoxetic acid enhancement.

METHODS

Nine patients with hepatic sclerosed hemangiomas and 36 patients with cavernous hemangiomas (control group) who underwent gadoxetic acid-enhanced magnetic resonance imaging were included. Qualitative values (imaging findings and enhancement pattern [typical vs atypical enhancement]) and quantitative values (apparent diffusion coefficient) were evaluated.

RESULTS

Patients with sclerosed hemangiomas showed significantly more irregular tumor margin on hepatobiliary phase images, peritumoral arterial enhancement, and a lower proportion of hyperintensity on heavily T2-weighted images compared with controls (all P values <0.05). In addition, the sclerosed hemangioma group had significantly more frequent atypical enhancement patterns than did the control group (88.9% vs 33.3%; P = 0.006). However, the mean apparent diffusion coefficient value of hemangiomas was not significantly different between the 2 groups (P = 0.639).

CONCLUSIONS

Gadoxetic acid-enhanced magnetic resonance images can help in differentiating between hepatic sclerosed hemangiomas and cavernous hemangiomas.

Differentiation between inflammatory myofibroblastic tumor and cholangiocarcinoma manifesting as target appearance on gadoxetic acid-enhanced MRI

PURPOSE

To determine the differential features of inflammatory myofibroblastic tumor (IMT) and intrahepatic cholangiocarcinoma (ICC) manifesting as target appearance on gadoxetic acid-enhanced MRI.

METHODS

Twenty-seven patients with 36 IMTs (1.2-6.0 cm) and 34 patients with 34 ICCs (1.5-6.0 cm) who underwent gadoxetic acid-enhanced MRI were enrolled in this study. Two reviewers evaluated morphology, signal intensity, and enhancement features of tumors on T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and gadoxetic acid-enhanced imaging.

RESULTS

As for 32 IMTs with target appearance, IMTs most commonly demonstrated early target appearance characterized by a peripheral hypointense rim on unenhanced T1WI (n = 27, 84.4%), central enhanced area with a hypointense rim on arterial phase (AP) and portal venous phase (PVP) (n = 29, 90.6%), and transitional phase (TP) (n = 28, 87.5%). Meanwhile, most of the ICCs showed homogeneous hypointensity on T1WI (100%), a hyperenhancing rim on AP, late target appearance on TP (n = 32, 94.1%) and HBP (n = 32, 94.1%). Target appearance on DWI appearing as hyperintensity with central hypointense area was seen in 2 IMTs and 32 ICCs. On T2WI, 24 IMTs (n = 24, 75.0%) displayed central iso- and peripheral hyperintensity and 27 ICCs (84.4%) showed layered hyperintensity with either brighter or darker area in center. The remaining six IMTs with no target were observed as cystic appearing nodules (n = 3) or ill-defined hypovascular nodules (n = 2) and fibrotic mass (n = 1).

CONCLUSION

IMTs often show early target appearance on unenhanced T1WI, and early dynamic phases of gadoxetic acid-enhanced MRI. Target appearance on later phases, such as TP and HBP, and DWI target appearance were commonly in ICCs, but rare in IMTs.

Technical advancements and protocol optimization of diffusion-weighted imaging (DWI) in liver

An area of rapid advancement in abdominal MRI is diffusion-weighted imaging (DWI). By measuring diffusion properties of water molecules, DWI is capable of non-invasively probing tissue properties and physiology at cellular and macromolecular level. The integration of DWI as part of abdominal MRI exam allows better lesion characterization and therefore more accurate initial diagnosis and treatment monitoring. One of the most technical challenging, but also most useful abdominal DWI applications is in liver and therefore requires special attention and careful optimization. In this article, the latest technical developments of DWI and its liver applications are reviewed with the explanations of the technical principles, recommendations of the imaging parameters, and examples of clinical applications. More advanced DWI techniques, including Intra-Voxel Incoherent Motion (IVIM) diffusion imaging, anomalous diffusion imaging, and Diffusion Kurtosis Imaging (DKI) are discussed.