Fibrosing mediastinitis

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 oesophagus.

It is characterised 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: commoner ~80% 5-6
  • diffuse: ~20%
Causes
  • idiopathic: most cases 12
  • Histoplasma capsulatum infection (histoplasmosis): common in the United States and often gives a localised pattern 8
  • Mycobacterium tuberculosis infection (pulmonary tuberculosis) 5
  • concurrent intrathoracic malignancy 5
  • sarcoidosis 14
  • radiation therapy
  • drugs, e.g. methysergide therapy 8
Associations
Plain radiograph

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. Other accompanying features include:

  • calcification (mediastinal and/or hilar) ~85% (commoner in localised type) 3
CT

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 localised disease
  • infiltrative region of 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
  • pulmonary infiltrates 2
MRI

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

  • T1: typically heterogeneous but overall iso-signal 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 affected region could be considered with localised disease. Some patients with the diffuse pattern show radiographic evidence of improvement with steroid therapy.

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Article Information

rID: 11089
System: Chest
Tag: cases
Synonyms or Alternate Spellings:
  • Mediastinal fibrosis
  • Sclerosing mediatinitis
  • Chronic sclerosing mediastinitis
  • Granulomatous mediastinitis
  • Fibrosing mediastinitis (FM)

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