Fibrosing mediastinitis

Clinical History

An asymptomatic 75-year-old woman underwent a preoperative chest radiograph.

Imaging Findings

The radiograph showed the presence of a great mass in the right paracardiac, located in the anterior mediastinum. A contrast-enhanced CT scan (mediastinal windows) which was taken, manifested an anterior mediastinal mass measuring 12 x 7 cm, soft-tissue attenuation with invasion to the adjacent structures. Calcifications were not observed. The fine needle biopsy of this lesion was performed, by obtaining a smear with extensive areas of fibrosis. The definitive diagnosis was made with biopsy. It was found that this tumor had infiltrated anterior thoracic wall.

Discussion

Fibrosing mediastinitis is a rare benign disorder characterized by the proliferation of dense fibrous tissue that infiltrates the normal mediastinal fat planes and encases or invades the adjacent structures. It affects patients who are typically young (30–40 years old) without a predilection for either sex. There may be two types of fibrosing mediastinitis, focal and diffuse. The focal type is probably caused by an abnormal immunological response to a previous H.capsulatum infection, although other implied infections exist(tuberculosis, aspergillosis, mucormycosis, blastomycosis and cryptococcosis). The diffuse type is usually associated with autoimmune disease, radiation therapy, trauma, Hodgkin disease and drug therapy with methysergide maleate. The clinical manifestations are related to the obstruction of vital mediastinal structures. The differential diagnosis of fibrosing mediastinitis includes other lesions of the mediastinum, such as lymphoma, thymoma, metastatic carcinoma, lung cancer, and germinal cell neoplasms. The radiological features of fibrosing mediastinitis usually manifest on chest radiographs as a nonspecific widening of the mediastinum, with the distortion and obliteration of normally recognizable mediastinal interfaces or lines. In CT scans, the condition typically manifests as the presence of a mediastinal mass, with soft-tissue attenuation that can invade the adjacent structures. The focal pattern, seen in 82% of the cases, manifests as a mass of soft-tissue attenuation that is frequently calcified and is usually located in the right paratracheal or subcarinal regions or in the hila. The diffuse pattern, seen in 18% of the cases, manifests as a diffusely infiltrating, noncalcified mass that affects multiple mediastinal compartments. On MR imaging, it typically manifests on T1-weighted MR images as a heterogeneous, infiltrative mass of intermediate signal intensity. Its appearance on T2-weighted MR images is more variable, as regions of both increased and markedly decreased signal intensity are frequently seen in the same lesion. The fine needle biopsy of these lesions is frequently found to be insufficient for the diagnosis by the extensive areas of fibrosis. The definitive diagnosis requires a biopsy.

Differential Diagnosis List

Final Diagnosis

Fibrosing mediastinitis.

URL:	https://www.eurorad.org/case/3313
DOI:	10.1594/EURORAD/CASE.3313
ISSN:	1563-4086