B41. Diseases of the chest wall. Tumors of the mediastinum.

Pectus excavatum

Pectus excavatum is a deformity of the sternum where the sternum protrudes inward. It’s the most common deformity of the anterior chest wall. It’s mostly idiopathic but may be associated with connective tissue disorders like Marfan syndrome. It’s more common in males. It's sort of the opposite of pectus carinatum.

May be present at birth (at which case it usually worsens during the rapid growth of adolescence), or it may occur later. The deformity is mostly a cosmetic problem, but in compression of the lung may cause dyspnoea, decreased exercise intolerance, atelectasis, and recurrent respiratory infections. The chest wall may be asymmetric.

Diagnosis and evaluation

To evaluate the severity during consideration for surgery, a CT scan must be made to calculate the Haller index (pectus severity index). See this image for details. Two distances in the thoracic cavity are measured (A and B), and the Haller index is calculated as A/B. A Haller index of > 3,5 is an indication for surgery.

Management

The optimal time for surgery is the age of ~15. Surgery is not performed at much younger ages due to the importance of being able to follow instructions regarding the postoperative period (not lifting heavy, no sports, etc.). Surgery is not performed after age of 30 due to rigidity of the chest wall.

Surgery involves implantation of a metal bar just underneath the sternum, which elevates it. This procedure is called the modified Nuss operation. Each lung is intentionally collapsed sequentially during the operation to prevent the metal bar from puncturing it. The procedure is guided by video, achieved by inserting a camera through the chest wall. Elevation of the sternum with a metal bar is possible due to the soft cartilages of children. The metal bar is removed 2 – 3 years later (as it cannot grow with the body).

Possible complications of surgery include dislocation of the metal bar, haemothorax, etc.

If surgery is not indicated, the patient should receive physiotherapy and exercises to grow the chest wall muscles, which will improve the deformity.

Pectus carinatum

Pectus carinatum (pigeon chest) is sort of the opposite of pectus excavatum, where the sternum protrudes outward. It is less common than pectus excavatum. It rarely causes symptoms other than cosmetic concerns.

In mild or moderate cases, a brace can be used. In severe cases, surgery is necessary.

Mediastinal tumours

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.