CT and 18FDG-PET/CT findings in progressive mediastinal idiopathic fibrosis as a benign mimicker of esophageal carcinoma: a case report

Abstract

Idiopathic mediastinal fibrosis, also called sclerosing or fibrosing mediastinitis, is a very rare and aggressive fibroinflammatory process characterized by fibrous tissue proliferation in the mediastinal region. Herein, we present a rare case of idiopathic mediastinal fibrosis presenting with esophageal obstruction, most likely associated with immunoglobulin G (IgG4)-related disease, affecting the posterior mediastinum with intrapulmonary infiltration. Computed tomography revealed a narrowed lumen and thickened wall of the distal esophagus surrounded by a necrotic mass with infiltration into the nearby structures, suggesting a locally advanced malignant process. Positron emission tomography revealed intense accumulation of 18F-fluorodeoxyglucose, indicating an active inflammatory component, which complicates further differential diagnosis of mediastinal masses. Thoracoscopic biopsy and immunohistochemical analysis confirmed a fibroinflammatory process with perivascular lymphoid cell infiltration that was cluster of differentiation (CD)3 (++) and CD20 (++), with massive numbers of IgG4-immunoreactive plasma cells. Although a benign condition, sclerosing mediastinitis is a close mimicker of esophageal carcinoma, which cannot be differentiated by computed tomography or positron emission tomography and must be considered in a differential diagnosis.

Keywords: Idiopathic mediastinal fibrosis; IgG4-related disease; case report; computed tomography; differential diagnosis; esophageal carcinoma; positron emission tomography.

Figure 1.

Computed tomography of the chest, axial view, showing a solid, infiltrative mass in the mediodistal esophagus with luminal obstruction and spread to the pericardium, aortic wall, and mediastinal pleura (a). Coronal scan showing a narrowed esophageal lumen and a mass that resembled esophageal carcinoma (b).

Figure 2.

Histopathological examination showing mainly fibroinflammatory changes with low cellularity, strong collagenases, and dense fibrohyaline areas within a polymorphic inflammatory infiltrate with a predominance of plasmacytes and eosinophils (×4, hematoxylin and eosin).

Figure 3.

Immunohistochemical findings showing oligocellular infiltrate with occasional strong perivascular infiltration and lymphoid cells with moderate immunoreactivity: CD3++ (a) and CD20++ (b). Some areas of infiltration are positive for fascin (c) and, rarely, for EMA (d). Abundant cells that are immunoreactive for IgG4 are visible (e, f) (×4). CD3, cluster of differentiation 3; CD20, cluster of differentiation 20; EMA, epithelial membrane antigen; IgG4, immunoglobulin G4.

Figure 4.

Follow-up CT 2 months after the initial diagnosis showing disease progression. Axial and coronal CT images show a large mediastinal, necrotic, mass that communicates with the esophageal lumen (the white arrow indicates a defect in the esophageal wall) and fistulization with peripheral airways of the right lower lung lobe (a, b). Pneumonic foci of lung parenchyma are also seen (c). CT, computed tomography.

Figure 5.

FDG PET-CT: PET, CT, combined PET-CT, and MIP images showing intense FDG uptake in a soft tissue mass abutting the lower esophagus (SUVmax: 20.6). Air bubbles and communication with the esophageal lumen are visible; infiltration into the upper abdomen is visible. FDG PET-CT, 18-fluorodeoxyglucose positron emission tomography-computed tomography; MIP, maximum-intensity projection; SUVmax, maximum standardized uptake value.