Mediastinal tumour

Many tumours can originate from or spread to the mediastinum.

• Anterior mediastinum
  • Thymoma (most common)
  • Germ cell tumours (teratoma, seminoma)
  • Lymphoma
  • Substernal thyroid tumour or goitre
• Middle mediastinum
  • Developmental cysts (bronchogenic, pericardial, etc.)
  • Lymphoma
  • LN metastases
• Posterior mediastinum
  • Neoplasms arising from nerve sheaths, like neurofibroma (most common)
  • Neoplasms arising from sympathetic ganglia, like neuroblastoma
  • Neoplasms arising from paraganglionic tissue, like paraganglioma

The most common mediastinal mass is involvement of the mediastinum by bronchogenic lung cancer.

The "4 T’s of mediastinal masses"

• Thymoma
• Teratoma
• Thyroid neoplasm
• “Terrible” lymphoma

Clinical features

Mediastinal masses are frequently asymptomatic, only discovered incidentally on imaging. However, they can also cause a variety of different symptoms:

• Dysphagia
• Airway compression
• Hoarseness – due to affection of recurrent laryngeal nerve
• Elevated hemidiaphragm – due to affection of the phrenic nerve
• Horner syndrome – due to affection of the sympathetic chain
• Superior vena cava syndrome
• Haemoptysis

Thymoma is frequently associated with myasthenia gravis, and patients diagnosed with thymoma should be evaluated for this.

Diagnosis and evaluation

X-ray (both AP and lateral) is the best initial test for mediastinal disorders, and may show a widened mediastinal shadow. It should be followed up by a contrast CT scan if any masses are found. The CT can give information on the density of the mass, which is important for the differential. If a malignancy is suspected, PET/CT should be made.

The final diagnosis requires histology, and so a biopsy is required. This can be achieved by transcutaneous FNAB, bronchoscopy, mediastinoscopy, endoscopic (oesophageal) ultrasound, thoracoscopy, or by thoracotomy.

Treatment

Almost all mediastinal masses are indications for surgical removal. One exception is the seminoma, which is highly sensitive to chemo and radiotherapy and is therefore not operated. Another exception are the cysts, which are only operated if they’re growing or causing symptoms.