Fibrosing mediastinitis

Last revised by Mostafa Elfeky on 30 Sep 2023

Fibrosing mediastinitis is a rare non-malignant acellular collagen and fibrous tissue proliferative condition occurring within the mediastinum. On imaging, the condition can sometimes mimic malignancy.

Although it can potentially present at any age, it typically presents in young adults.

Affected patients usually present with signs and symptoms of obstruction or compression of the superior vena cava, pulmonary veins or arteries, central airways, or esophagus and may complain of broncholithiasis

It is characterized by chronic inflammation and excessive fibrosis of mediastinal soft tissues. This may lead to compression and sometimes occlusion of mediastinal structures. There are two main pathological types:

  • focal: ~80% 5,6

  • diffuse: ~20%

  • idiopathic: most cases 12,  thought to be a form of IgG4-related disease 17

  • infection:

    • Histoplasma capsulatum infection (histoplasmosis): common in the United States and often gives a localized pattern 8

    • Mycobacterium tuberculosis infection (pulmonary tuberculosis) 5

  • concurrent intrathoracic malignancy 5

  • sarcoidosis 14

  • radiation therapy

  • drugs: e.g. methysergide therapy 8

Can be subtle and may be seen as a non-specific widening of the mediastinum. There can be distortion and obliteration of normally recognisable mediastinal interfaces or lines. There may also be mediastinal and/or hilar calcification (~85%) which is more common in the localized type 3.

The exact appearance can be variable and dependent on the pattern of involvement. Typically affects the middle mediastinum and may show:

  • mediastinal or hilar mass: especially in localized disease

  • soft-tissue attenuation which obliterates normal mediastinal fat planes and encases or invades adjacent structures: diffuse form

Other findings include:

  • calcifications of the central mass or associated lymph nodes: especially if there has been preceding histoplasmosis

  • tracheobronchial narrowing 2,4

  • areas of pulmonary opacity 2

  • endobronchial calcification with atelectasis of the associated segment or lobe

  • pleural thickening and calcification 

  • associated pulmonary granuloma reflecting the original cause like healed granuloma from tuberculosis or histoplasmosis 

  • engorged bronchial arteries due to vascular compromise 

  • local lung changes: prominent interstitial pattern (segmental and/or diffuse) and crazy paving secondary to compressed veno-lymphatic pathways.

The pattern of involvement is essentially similar to CT. Signal characteristics include:

  • T1: typically heterogeneous but overall isointense to muscle 

  • T2: variable with both high 3 and low 2,3 signal within the same lesion

  • T1 C+ (Gd): may show heterogeneous enhancement

Fibrosing mediastinitis can have an unpredictable course, with both spontaneous remission or exacerbation of symptoms being reported.

It usually tends to be slowly progressive. There are three possible avenues for treatment: systemic antifungal or corticosteroid treatment, surgical resection, and local therapy for complications.

Surgical resection of the affected region could be considered with localized disease. Some patients with the diffuse pattern show radiographic evidence of improvement with steroid therapy.

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