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MEDIASTINAL TUMORS�

Assoc. Prof. Edwin OSENI-MOMODU

College of Medicine and Health Sciences�Bingham University Teaching Hospital�Jos�6 April 2016�

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  • The mediastinum refers to the central area in the chest between the thoracic inlet and the diaphragm,
  • between the right and left pleural surfaces and
  • which extends from the inner aspect of the sternum to the vertebral column.

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  • It contains the heart, great vessels, trachea and the oesophagus,
  • is arbitrarily subdivided into 3-5 compartments depending on the authors: We would use 5 viz (superior, inferior, anterior, middle and posterior).
  • Much of the regional lymph node chains draining the chest and its organs are also found in the mediastinum.

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  • Various surgical procedures to approach structures and particularly lymph nodes in the mediastinum are performed usually as diagnostic procedures.

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  • The surgical approach when mediastinal tumours require resection depends on the antomical location of the tumour and
  • includes median sternotomy

for anterior mediastinal pathology,

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  • thoracotomy or VATS for posterior mediastinal pathology and transcervical (neck incisions) for superior mediastinal pathology.
  • The middle mediastinum can usually be approached through thoracotomy or VATS.
  • VATS=Video-assisted thoracoscopic surgery (VATS)

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PRIMARY TUMOURS OF THE MEDIASTINUM

  • Thymoma, neurogenic tumors, germ cell tumors and lymphoma are the usual primary tumors of the mediastinum.

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THYMOMA:-

In adult

  • This is the most common mediastinal tumour, accounting for 25% of the total and is derived from the thymus gland

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  • Thymomas vary in behaviour from benign to aggressively invasive as reflected in the Masaoka classification system used to stage thymomas.

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Mediastinal pathology. Subdivisions of the mediastinum with the most common mediastinal masses.

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Computed tomography scan showing a thymoma presenting

as a mediastinal mass.

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Computed tomography scan showing a right-sided paravertebral

neurogenic tumour.

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Video-assisted thoracoscopic surgery (VATS) image of a neurogenic tumour attached to the posterolateral chest wall prior to excision.

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  • They are often related to myaesthenia gravis (MG), a neuromuscular condition which can have a high associated incidence of thymomas,
  • and interestingly may respond to excision of the thymus gland even when the gland has no associated thymoma present.

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  • The only reliable indicator of malignancy is capsular invasion.
  • Diagnosis and treatment are best achieved by complete thymectomy, which is usually performed as a median sternotomy.

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  • However, if the thymoma is small or when the patient has MG and the thymus is being excised as a treatment, a transcervical approach with or without an additional VATS procedure can be performed.
  • Classification according to Masaoka

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GERM CELL TUMOUR.

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  • The anterior mediastinum is the most common site of extragonadal germ cell tumours.
  • They account for 13 per cent of all mediastinal masses and cysts and contain elements from all three cell types (mesoderm, endoderm and ectoderm).

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  • They tend to present in young adults and 75 per cent are benign and cystic, although they may cause compression of neighbouring structures;
  • hence, dermoid cysts are best excised.

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  • Malignancy is suspected if elevated levels of
  • serum alpha-fetoprotein,
  • human chorionic gonadotrophin and
  • carcinoembryonic antigen are detected.

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  • After initial treatment with chemotherapy, a patient with tumour marker normalisation and a persistent mass on CT may be considered for surgical resection.
  • If tumour markers fail to normalise,further chemotherapy is usually offered.

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LYMPHOMA.

  • lymphoma is a common cause of a mediastinal mass lesion, particularly the anterior mediastinum, and
  • can lead to superior vena cava obstruction or other symptoms of local compression.

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  • The main treatment is chemotherapy, and
  • surgery is rarely required apart from obtaining tissue for diagnosis.

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MESENCHYMAL TUMOURS.

  • Lipomas are common in the anterior mediastinum. Other mesenchymal tumours are very rare.

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THYROID.

  • Ectopic thyroid tissue (and parathyroid) may be found in anterior mediastinum, but
  • usually the the mass is an extension of a thyroid lesion (Retrosternal Goitre).

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  • Excision of retrosternal thyroids may be required if there is local airway compression and stridor and
  • can be performed via a transcervical incision, but occasionally median sternotomy may be required.

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NEUROGENIC TUMOURS.

  • These may derive from the sympathetic nervous system or the peripheral nerves and
  • are more prevalent in the posterior mediastinum.

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  • They may be painful but are more often discovered accidentally on routine chest radiography and can be quite large (Slide 10).
  • They include NEUROBLASTOMA in childhood, ….

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and

  • SCHWANNOMAS and NEUROfiBROMAS in adults, which are usually benign.
  • PHAEOCHROMOCYTOMA arises from the sympathetic chain and produces the characteristic endocrine syndrome.

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  • Excision of neurogenic tumours is generally recommended particularly if the patient is developing symptoms.
  • This can be performed through a thoracotomy, though for smaller tumours a VATS approach can be used ().

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  • Enlarged mediastinal lymph nodes are commonly involved by metastatic tumour mimicking a primary mediastinal lesion.

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  • Symptoms are generally secondary to compression or invasion of a structure within the mediastinum.
  • Surgery, mediastinoscopy, is reserved for diagnosis only.

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OTHER CONDITIONS OF THE MEDIASTINUM

  • Many of the primary tumours, such as neurogenic tumours and germ cell tumours, can present as cysts or have a cystic quality.

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  • In addition, the mediastinum can contain other Cysts often with an embryological aetiology.
  • Thymic cysts, pericardial cysts, bronchogenic and foregut cysts can all present asymptomatically or with local compression ().

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  • Surgical excision is recommended if diagnosis is unclear or the patient has symptoms.

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References:

  • BAILEY AND LOVES’S

“Short Practice of Surgery”,

26th International Students’ Edition

  • SCHWARTZ’S

Principle Surgery,

9th Edition- Chm

  • SABISTON

Textbook of Surgery,

18TH Edition-chm

  • BAJA’S

Principles And Practice Of Surgery,

(Volumes I & Ii),

Fifth Edition Of

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