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
Introduction
Inflammatory myofibroblastic tumour (IMT), formerly known as an inflammatory pseudotumour, is a distinctive, rare neoplasm composed of myofibroblastic mesenchymal spindle cells accompanied by an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils.1 IMT is now considered a possible neoplastic counterpart to an inflammatory pseudotumour, which may occasionally show aberrant expression and gene translocation of anaplastic lymphoma kinase (ALK).2 Some studies of hepatic IMTs have reported that surgical resection may be of limited value due to a favourable prognosis.3, 4, 5 However, findings from images of hepatic IMTs are often unclear. Making a preoperative diagnosis is difficult because IMTs can mimic various benign and malignant diseases, such as liver abscess, hepatocellular carcinoma, intrahepatic mass-forming cholangiocarcinoma, and metastasis.3, 6 Therefore, accurate diagnosis of hepatic IMTs using preoperative imaging methods or biopsy is essential to avoid unnecessary surgical resection because treatment and prognosis differs significantly from the other disease entities that mimic IMTs on imaging studies.
Recently, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (gadoxetic acid; Primovist, Bayer Healthcare, Berlin, Germany) has been widely used as an magnetic resonance imaging (MRI) contrast agent to obtain information from extracellular and liver-specific hepatocellular imaging phases.7 In addition, diffusion-weighted (DW) MRI is increasingly applied as an liver imaging technique to differentiate benign and malignant diseases based on the measurement of extracellular water diffusion.8
Although several case studies report imaging findings of hepatic IMTs with ultrasonography (US), computed tomography (CT), MRI, or 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET),9, 10, 11, 12, 13, 14 to the authors' knowledge, no study of hepatic IMTs has used gadoxetic acid-enhanced and DW MRI with FDG-PET/CT. Hepatic IMTs are generally benign given their propensity for regression15, 16 and no studies have focused on volume changes of IMTs over time with the goal of determining appropriate time intervals for follow-up imaging. The aim of the present study was to assess gadoxetic acid-enhanced and DW MRI findings of liver IMTs using combined FDG PET/CT, and evaluate the clinical course with volume change on follow-up.
Section snippets
Materials and methods
This study was designed as a single-centre, retrospective analysis. The institutional review board approved this study and informed consent was waived.
Clinical and laboratory findings
The clinical characteristics of 13 patients with 18 IMTs are listed in Table 2. Most patients (9/13, 69.2%) were diagnosed incidentally during work-up for other diseases or routine health examinations with abdominal ultrasonography. The most common clinical symptom was fever (n = 3) followed by abdominal discomfort (n = 1). Abnormal laboratory findings from the 13 patents were elevation of C-reactive protein (CRP) (n = 5), mildly elevated liver enzymes (n = 3), leukocytosis (n = 2), increase in
Discussion
The present results demonstrated the utility of gadoxetic acid-enhanced MRI with DW imaging and FDG PET/CT of hepatic IMTs. The results also showed the clinical significance of regression on follow-up. Although hepatic IMTs showed varied morphological features and mimicked malignant tumours with diffusion restriction on MRI and increased uptake of FDG, hepatic IMTs showed rapid regression on follow-up without tumour recurrence or distant metastasis.
The most common symptoms and abnormal
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