Common topics in thoracic surgery
Thoracic surgical topics discussed in this chapter are related to disorders of the chest wall, pleural space, lungs and mediastinum. Other conditions managed by general thoracic surgeons include diseases of the oesophagus and chest trauma. Both of these topics are presented in Chapters 10, 11 and 45.
Presentation of thoracic disorders
Common thoracic symptoms include cough, chest pain, shortness of breath (on exertion or at rest), excessive or abnormal sputum production, haemoptysis, wheeze or stridor. Many conditions (especially neoplasms) are asymptomatic and are first detected on chest X-ray.
On examination, the patient may appear quite normal or severely short of breath (e.g. from a spontaneous pneumothorax). Clues to intrathoracic problems may be found in the other parts of the body such as clubbing of the finger nails, peripheral cyanosis and lymphadenopathy. The jugular venous pressure may be elevated (e.g. from neoplastic superior vena caval obstruction or tension pneumothorax) and the trachea may be deviated from the midline. Signs found in the chest in some common thoracic conditions are given in Table 59, “Physical signs in thoracic disease”. Again, in some conditions, the findings on examining the chest can be completely normal.
|Chest wall movement||Mediastinum and trachea||Tactile voca fremitus||Percussion note||Breath sounds|
|Large pleural effusion above||Reduced on affected side||Shift to opposite side||Absent||Stony dull||Absent. May be bronchial, fluid level|
|Large pneumothorax||Reduced on affected side||Shift to opposite side||Decreased||Increased||Decreased|
|Massive lung collapse||Reduced on affected side||Shift to affected side||Absent||Dull||Decreased|
|Pneumonic consolidation||Reduced on affected side||Central||Increased||Dull||Bronchial|
|Advanced emphysema||Reduced on both sides ‘barrel chest’||Central||Decreased||Increased||Decreased|
Non-invasive diagnostic investigations
All patients with a suspected thoracic problem should have an erect postero-anterior and lateral chest X-ray. This will help define the location and extent of the problem.
Pulmonary function testing and arterial blood gases
Pulmonary function tests (PFTs) help to define the degree of respiratory impairment on presentation, the amount of functional reserve, and hence the ability of the patient to tolerate lung surgery and, at follow-up, the response to therapy. There are two major types of PFT:
- those that assess the movement of air in and out of the lungs (e.g. forced expiratory volume in 1 second, forced vital capacity, peak flow, total lung capacity, residual volume)
- those that measure the ability to transfer gas across the alveolar-capillary membrane (e.g. tests of carbon monoxide diffusing capacity).
When considering surgical therapy for a given patient, it may be evident that the patient has insufficient ventilatory capacity to withstand a chest wall incision or a major pulmonary resection, and alternative therapies will need to be offered.
Arterial blood gas analysis is an important investigation in patients with acute and chronic thoracic conditions. Parameters measured include PaO2, PaCO2, pH, bicarbonate level and arterial oxygen saturation.
High-resolution images of the chest wall, pleural space, lungs and mediastinum are provided in cross-section.Tissue density is quantified and a fairly accurate map of pathological lesions throughout the chest is obtained. Serial computed tomography (CT) scanning is helpful in following up suspicious lesions. Percutaneous needle biopsy of pulmonary or pleural lesions is frequently performed under CT guidance. The upper abdomen should also be scanned in patients with known or suspected pulmonary malignancy to assess the liver and adrenal glands, which are common sites for secondary deposits. Magnetic resonance imaging (MRI) is also used in centres where it is available.
Invasive and operative investigations
Diagnostic bronchoscopy, using a flexible or rigid instrument, provides direct visualisation of airway lesions for biopsy. Lesions of the lung parenchyma or lymph nodes in the subcarinal space may be biopsied using a transbronchial technique. Most commonly, diagnostic bronchoscopy is performed by respiratory physicians with the flexible bronchoscope. This is performed using a combination of topical anaesthesia and intravenous sedation. More difficult and potentially complicated situations are handled by thoracic surgeons in the operating room. Occasionally, therapeutic rigid bronchoscopy is required to control massive haemoptysis, to remove aspirated foreign bodies, or to clear retained inspissated sputum leading to postoperative lung or lobar collapse.
The mediastinoscope is a lighted cylindrical instrument used to biopsy paratracheal and subcarinal lymph nodes, most commonly in the work-up to stage a patient with known or suspected lung cancer. This investigation usually precedes any major pulmonary resection for lung cancer. It is also used in the investigation of mediastinal masses. The instrument is introduced via a transverse suprasternal incision and passed caudally in a plane deep to the pretracheal fascia. The mediastinoscope passes close to the superior vena cava (to its right), the innominate artery and arch of aorta (in front) and the recurrent laryngeal nerves (to the left and right posterolaterally). Care should be taken to avoid biopsying vascular structures such as the superior vena cava, azygos vein and pulmonary artery. Access is obtained to the upper middle and posterior mediastinum except for the subaortic area below the aortic arch, which is best approached via an anterior mediastinotomy.
Anterior mediastinotomy is a left parasternal, intercostal incision employed to access tissue from the anterior mediastinum (e.g. thymic lesions). A short horizontal or vertical incision may be made either in the second or third intercostal space or by resecting a costal cartilage. A left anterior mediastinotomy allows excellent access to the subaortic lymph nodes, the primary site of spread for tumours in the left upper lobe.
Pleural aspiration and biopsy
When a pleural effusion is present (Chest X-ray showing a large left-sided pleural effusion.), pleural fluid may be aspirated (thoracocentesis) using a needle and syringe. Cytological, microbiological and biochemical analyses may provide a clue as to the cause of the pleural effusion. Pleural biopsy can be performed at the same time using an Abram's needle.
Many chest wall, pleural, pulmonary or mediastinal masses can be biopsied under CT control. This allows a tissue diagnosis to be made prior to any surgical intervention. It must be noted that a negative biopsy result does not exclude malignancy.
Thoracoscopy, the thoracic equivalent of laparoscopy, uses cameras, telescopes and television monitors to inspect the pleural space, lung and mediastinum. Biopsy material may be taken from lesions in all these areas. The most common application is for lung and pleural biopsy. Three ports made by 2-cm incisions in the chest wall are used in the hemithorax, one for the telescope with the camera and light source and two for the instruments. Some therapeutic procedures, especially the management of recurrent spontaneous pneumothorax and thoracodorsal sympathectomy, are carried out using video-assisted thoracoscopy (VATS) techniques.
Rarely, a diagnostic thoracotomy is required when less invasive procedures are inappropriate or have failed to provide a diagnosis. Access is obtained to the mediastinal lymph node groups, the great vessels, oesophagus, lung and pericardium for tissue sampling. Frozen section analysis usually provides an immediate diagnosis and this result will determine what further intraoperative measures, if any, are required.
Basic thoracic surgical techniques
Pleural aspiration may be used in diagnosis, as the primary treatment of a pleural collection or as a preliminary measure prior to the insertion of a chest tube for the drainage of a pleural effusion. The presence of fluid should be confirmed on physical examination and chest X-ray (Chest X-ray showing a large left-sided pleural effusion.) prior to commencement.With the patient in a comfortable position sitting up, the chest is widely prepared and the puncture site chosen. Local anaesthetic is infiltrated liberally down to the pleura. The aspiration needle is inserted at the upper edge of the rib and up to 1 L can safely be removed at a given sitting. Upon completion, the needle is removed and a small dressing applied. A chest X-ray is then performed to exclude a pneumothorax.
Chest tube insertion and management
Common indications for chest tube insertion include spontaneous pneumothorax, tension pneumothorax, a large pleural effusion or empyema and post-traumatic haemothorax. Chest tubes are placed routinely at the completion of intrathoracic operations. In all situations, it is mandatory that an experienced operator insert the tube, because a badly performed placement is extremely dangerous.
The usual site for insertion is the fourth or fifth intercostal space in the mid-axillary line, but for the drainage of specific air, fluid or blood collections, the appropriate location on the chest wall should be chosen. The patient should be in a comfortable and relaxed position, and adequate local analgesia is essential. Following antiseptic skin preparation and infiltration of local anaesthetic into the skin, muscle layers and pleura, a skin incision is made over the middle of the chosen intercostal space. The incision is deepened using blunt dissection (with artery forceps) down to and through the pleural layer. Final dissection into the pleural space is made with a finger, and the point of entry can be widened by opening the artery forceps widely in two directions at 90. to each other. If a tension pneumothorax is present this manoeuvre will result in a rush of air and immediate relief for the patient. The chest drain is inserted through the chest wall and firmly retained in position with strong non-absorbable sutures. The drain tube is then connected to an underwater drainage system. In almost all situations the drain should be connected to wall suction, usually high flow and low pressure (e.g. 20 cm of water). A chest X-ray must always be performed following chest tube insertion to confirm tube position and to exclude a large pneumothorax.
A chest drain should be removed only when all air leak and fluid drainage has ceased. The lung should be fully expanded on chest X-ray. A chest tube must never be ‘clamped’ prior to removal. The patient is asked to breathe in maximally while the tube is briskly removed and an occlusive dressing placed over the wound.
Tracheostomy is the making of a surgical opening in the trachea. Recent modifications have included percutaneous tracheostomy and minitracheostomy.
Indications for tracheostomy
The common indications for tracheostomy are listed in Indications for tracheostomy. The benefits of a tracheostomy are that it overcomes respiratory tract obstruction, allows control of secretions, reduces respiratory dead space and allows mechanical ventilation other than via an endotracheal tube.
An elective surgical tracheostomy is performed in the operating room usually under general anaesthesia. Alternative settings include the intensive care unit (percutaneous tracheostomy) or the bedside (minitracheostomy). Via a midline lower cervical incision, a stoma is created at the level of the second and third tracheal rings through which a cuffed tracheostomy tube is placed. The lower airway is suctioned with a fine catheter and, after the tube is secured in position and the cuff inflated, ventilation can commence.
The complications of tracheostomy are listed in Complications of tracheostomy.
Posterolateral thoracotomy is the standard approach for major pulmonary resections. The incision is located below the inferior angle of the scapula, the latissimus dorsi is divided and the pleural space is entered along the superior surface of the fifth or sixth rib.
Lateral thoracotomy is used when only limited access is required, such as in the operative treatment of recurrent pneumothorax. The incision is made between the anterior and posterior axillary lines.
Anterior thoracotomy is used for open lung biopsy. An incision is made beneath the male nipple or female breast. There is a low incidence of post-thoracotomy neuralgia using this approach.
Median sternotomy or ‘sternal split’ gives excellent access to the anterior mediastinum, pericardium, heart and great vessels. Anterior mediastinal tumours (e.g. thymomas) and apices of each lung (in lung volume reduction operations) can be removed via this approach.
Common thoracic disorders
A classification of common chest wall conditions is given in Classification of chest wall conditions. Chest injuries are presented in Chapter 45. Soft tissue tumours and primary bone tumours will not be discussed further (see Soft tissue tumours and Diseases of bone and joints).
In pectus excavatum or ‘funnel chest’, there is a variable amount of depression of the sternum, lower costal cartilages and ribs. Frequently asymmetric, the deformity may displace the heart into the left chest. Heart and respiratory function are seldom impaired. Surgery, when indicated, is entirely cosmetic to correct the deformity.
In pectus carinatum or ‘pigeon chest’, the opposite deformity exists, where the sternum protrudes forward like the keel of a boat. Again, surgical correction is possible if the deformity is cosmetically unacceptable.
Secondary chest wall tumours
Involvement of the ribs and sternum by secondary tumours far exceeds that by primary bone tumours. Direct extension to the chest wall may occur in breast or lung carcinomas. Chest wall mestatases are often multiple and commonly originate in the lung, prostate, kidney, thyroid, stomach, uterus or colon. Tumours with multiple chest wall secondary deposits usually have a very poor prognosis.
Chest wall infections
De novo infections of the chest wall are extremely rare, and currently infection is most associated with a recent sternotomy or thoracotomy wound. Risk factors for post-operative wound infection include diabetes and morbid obesity. Abscesses can occur within the soft tissue planes and very rarely an empyema thoracis can ‘point’ through the chest wall (‘empyema necessitans’).
The pleural space is a potential cavity that normally contains negligible amounts of fluid due to equilibrium between its production and absorption. The accumulation of fluid within this space may be a manifestation of local or systemic disease.
Classification and aetiology
There are two types of pleural effusion: a transudate or exudate. The common causes of each are given in Causes of pleural effusion.
A transudate (specific gravity <1.016 and a protein content <3 g/dL) results from the altered production or absorption of pleural fluid. There is elevated systemic or pulmonary capillary pressures, lowered plasma oncotic pressure or lowered intrapleural pressure. There is no disorder of the pleural surfaces. An exudate (specific gravity >1.016 and a protein content >3 g/dL) is found in the presence of diseased pleural surfaces or lymphatics where there is increased capillary permeability or lymphatic obstruction.
Pneumonia of any cause may be complicated by the formation of a pleural effusion. Should pus form within the pleural space, the collection is known as an empyema thoracis. Currently, the most common cause of a post-pneumonic pleural effusion and empyema is bacterial infection.
Malignant pleural effusions can result from secondary pleural deposits, extension of the primary (lung) tumour to the pleural surface or lymphatic obstruction. Metastatic lung or breast carcinoma is the most common cause of malignant pleural effusions, but other common primary sites include the ovary, colon and kidney. There are frequently associated pulmonary metastases, but in some instances the intrathoracic metastatic lesion may be confined to the pleural space. The effusions are often blood stained (serosanguineous), with positive cytology in up to 70% and a positive pleural biopsy in 80% of malignant effusions.
Chylothorax refers to the accumulation of chyle within the pleural space due to disruption of the thoracic duct. Very rarely a congenital anomaly of the thoracic duct and seldom from tumour involvement, chylothorax is usually the result of surgical trauma to the duct somewhere along its course.
Common symptoms of a pleural effusion include pleuritic chest pain, shortness of breath, cough and haemoptysis (malignant effusion). The physical signs of a large pleural effusion are shown in Table 59, “Physical signs in thoracic disease”.
Investigations are listed in Investigations of pleural effusion. Chest X-ray (Chest X-ray showing a large left-sided pleural effusion.) will determine the extent of the effusion and may demonstrate underlying lung disease. Computed tomography scanning will also reveal significant intrathoracic disease. Diagnostic pleural aspiration will reveal the type of effusion based on appearance and cytological, microbiological and biochemical analysis. Pleural biopsy should be performed if the diagnostic pleural aspiration is unsuccessful or non-diagnostic. Should the effusion prove to be the result of a malignant process, it is important to adequately stage the disease prior to the commencement of therapy.
Therapy should be directed to any underlying cause such as pneumonia (antibiotics), congestive heart failure (diuretics), or malignancy (chemotherapy or radiotherapy).
The prognosis in patients with a malignant pleural effusion is poor; an average survival of 6 months follows diagnosis. Treatment of the effusion is therefore, at best, palliative. Closed chest tube drainage will provide short-term symptomatic relief, but the effusion usually re-accumulates upon tube removal. An attempt should be made to obliterate the pleural space (pleurodesis) to prevent the effusion reaccumulating. This may be achieved by introducing a sclerosing agent (e.g. talc) into the pleural space via a chest tube or at operation (VATS or thoracotomy) following drainage of the effusion.
Chylothorax usually responds to non-operative therapy; that is, chest tube drainage of the collection and measures to reduce chyle flow (no-fat diet, parenteral nutrition). Should the effusion persist or reaccumulate, operative intervention (thoracic duct ligation and/or pleurodesis) is indicated.
Empyema is managed in its early stages with dependent chest tube drainage. The pleural space may be irrigated with antiseptic solution. In chronic cases, a thick fibrous wall or cortex forms around the pus-filled pleural space. Treatment options include prolonged closed chest tube drainage, open chest tube drainage after resection of a segment of rib and open surgical decortication to remove the entire abscess wall. This releases the restricted chest wall and diaphragm and allows the lung to re-expand.
Pneumothorax refers to the presence of air within the pleural space. The air usually originates from the lung itself, but it may come from outside (after penetrating trauma) or from the oesophagus (after endoscopic perforation). The common types of pneumothorax are listed in Types of pneumothorax. Traumatic pneumothorax is discussed in the chapter on chest injuries (see Principles of trauma management).
Primary spontaneous pneumothorax
Primary spontaneous pneumothorax is the most common type of pneumothorax and usually results from the rupture of a tiny bleb or bulla at the lung apex. Occurring in tall, thin, young adults of either sex, it presents with acute chest pain and shortness of breath. Physical findings are given in Table 59, “Physical signs in thoracic disease”. Chest X-ray reveals an absence of peripheral lung markings and often a poorly defined line marking the border between lung and air (Chest X-ray showing a large right-sided spontaneous pneumothorax. Arrows show the collapsed lung edge.). The lung may be completely collapsed at the hilum.
If the pneumothorax is small, it may need no therapy other than observation and a repeat chest X-ray to confirm lung re-expansion or it may be aspirated with a needle. If the pneumothorax is large or under tension (discussed later), or if there is an associated pleural effusion, a formal chest tube should be inserted. As air is evacuated from the pleural space, the lung expands and presses against the chest wall, thereby sealing the site of the air leak. Once the tube stops bubbling it can be removed.
Secondary spontaneous pneumothorax
Secondary spontaneous pneumothorax occurs in the presence of significant underlying lung or pleural disorders such as primary or secondary malignancy, chronic airway disease (especially bullous emphysema) and pulmonary infections (bronchiectasis and lung abscess). The clinical features reflect the underlying disorder, and the presentation and initial management of the pneumothorax is as above.
A tension pneumothorax is present when the site of air leak in the lung acts as a one-way valve such that air enters the pleural space during inspiration and coughing but prevents its escape during expiration, thus raising the pressure within the pleural space. Such pressure or tension compresses the lung and shifts the mediastinum towards the other side. This compresses the normal lung and may also kink and distort the superior vena cava. The diagnosis should be suspected when signs of a large pneumothorax are associated with mediastinal shift and an elevated jugular venous pressure. This constitutes a medical emergency. A large-bore needle should be inserted to the affected side and if the diagnosis is correct will be met by the hiss of escaping air and a relief of the immediate problem. A formal chest tube should then be inserted.
Recurrent spontaneous pneumothorax
Approximately 30% of primary spontaneous pneumothoraces will recur and after a second episode this figure rises to 70%. If the same side has been affected twice or more, and especially if tension has occurred, a definitive procedure should be considered. Approaches via VATS or a limited thoracotomy include stapling of apical bullae to prevent further air leakage, and pleurodesis (either abrasive or chemical) or pleurectomy, which allows the visceral pleura to adhere to the parietal pleura or the bare chest wall.
Carcinoma of the lung
Carcinoma of the lung is the most common cause of cancer deaths in males and the second most common cause of cancer deaths after breast cancer in females. Usually occurring in patients older than 50, the overall incidence in both sexes continues to rise.
Cigarette smoking is the single most common predisposing factor. Environmental or occupational exposure to asbestos, arsenic, nickel, chromium and hydrocarbons also play a role. The highest geographical incidence is in parts of Scotland, suggesting a possible genetic influence.
The pathological types of lung carcinoma are listed in Pathological types of lung carcinoma.
Squamous cell carcinoma accounts for about 35% of all lung carcinomas. Most often centrally located, these tumours arise from metaplasia of the normal bronchial mucosa. Varying degrees of differentiation are seen depending on the presence of keratin, epithelial pearls, prickle cells, basal pallisading, cell size and mitotic activity.
Adenocarcinoma represents about 45% of lung carcinomas. More often found in women and located peripherally in the lung, the histopathology reveals acinar or papillary glandular elements. The tumour may form in long-standing scars (e.g. post-tuberculosis) and spreads via the bloodstream. Alveolar cell carcinoma is a highly differentiated form of adenocarcinoma. Tall columnar epithelial cells proliferate and spread along the alveolar walls. The tumour may be solitary, multinodular or diffuse (pneumonic). It may be indistinguishable from metastatic adenocarcinoma to the lung.
Large cell carcinoma comprises another 15% of malignant lung tumours. Peripherally located, there is abundant cell cytoplasm with a cellular pattern that is predominantly anaplastic.
Adenosquamous carcinoma is the most common of the mixed non-small-cell types of lung carcinoma. Tending to be peripheral in location, their behaviour is based upon the most prominent cell type.
Small cell carcinomas make up about 10% of malignant lung tumours. Mostly centrally located, they are the most malignant and carry the worst prognosis. The cells are small, round or oval in appearance (‘oat cell’). Ectopic formation of the hormones adrenocorticotrophic hormone (ACTH) or antidiuretic hormone (ADH) may occur. Lymphatic and pleural invasion is common. Seventy per cent of tumours have extrathoracic involvement at presentation.
Approximately 10–20% of lung cancers are asymptomatic and present as a chance finding on routine chest X-rays. Symptoms may be thoracic or extra-thoracic.
Thoracic symptoms include cough, haemoptysis, shortness of breath, chest pain (pleuritic or retrosternal), hoarseness of voice (involvement of recurrent laryngeal nerve), arm pain and weakness (Pancoast's syndrome; apical tumour involving brachial plexus).
Extra-thoracic symptoms include those of metastases (e.g. bone, central nervous system, liver, adrenals) and those of non-metastatic paraneoplastic syndromes. These include the production of ectopic ACTH, ADH and parathyroid hormone. Wrist and ankle pain due to hypertrophic osteoarthropathy and a variety of myopathies are also found.
Physical findings include hypertrophic pulmonary osteoarthropathy, fingernail clubbing, supraclavicular and cervical lymphadenopathy, signs of brachial plexus involvement, Horner's syndrome (ptosis, miosis, anhidrosis, enophthalmos from involvement of the cervical sympathetic ganglia), elevated jugular venous pressure and facial oedema (superior vena caval obstruction). In the chest there may be signs of a pleural effusion or lung collapse (Table 59, “Physical signs in thoracic disease”).
Investigations are listed in Investigations for lung carcinoma and will provide a tissue diagnosis and aid in determining the extent of intrathoracic disease. (A) Chest X-ray showing a right hilar lung cancer with collapse and consolidation of the right upper lobe. (B) Computed tomography scan showing the right hilar lung cancer.A and B show typical findings on chest X-ray and CT scan, respectively. If metastatic disease is suspected in sites such as bone or the brain, additional scans of these areas should be included so as to accurately stage the disease and to avoid unnecessary surgical intervention. Positron emission tomography (PET) scanning is showing promise in the evaluation of regional lymph nodes and also distant metastases. Radioactive tracers detect differences in metabolism between normal and malignant tissue. Metastatic disease has been found in up to 15% of lung cancers thought to have resectable disease. The number of these investigations required by a given patient is determined by the ease with which a tissue diagnosis and accurate staging is reached.
Staging of lung cancer
Staging of non-small-cell lung cancer is clinical and is based upon descriptors for the size and location of the primary tumour (T), the spread to lymph nodes within the thorax (N) and to the presence or absence of distant metastases (M). TNM subsets are grouped together into stages 0 through IV and these stages provide information about prognosis, allow a comparison of outcomes from different clinical series and also guide therapy.
Carcinoma of the bronchus presenting as a solitary pulmonary nodule (‘coin lesion’) in the lung periphery should be differentiated from the following:
- secondary tumours
- benign lung tumours (bronchial adenoma)
- non-specific granuloma
- tuberculous granuloma.
Unfortunately, two-thirds of patients are incurable at presentation owing to spread evidenced by one or more of the following:
- distant metastases
- a malignant pleural effusion
- involved cervical lymph nodes
- superior vena caval obstruction
- recurrent laryngeal nerve palsy.
If the patient has an otherwise resectable tumour and adequate respiratory reserve, surgical resection offers the only hope of long-term survival.
Surgical treatment consists of a thoracotomy with removal of the entire lung or lobe along with regional lymph nodes and contiguous structures. Where possible, lobectomy is the procedure of choice. Pneumonectomy is used if the tumour involves the main bronchus, extends across a fissure or is located such that wide excision is required. Survival following ‘curative’ resection is approximately 30% at 5 years and 15% at 10 years. The best results are found in squamous cell carcinoma followed by large-cell carcinoma and the adenocarcinoma. There are very few survivors of smallcell carcinoma beyond 2 years.
Radiotherapy may be ‘curative’ in patients with early stage disease unfit for surgical resection. However, the usual role for radiotherapy is in the palliation of pain from bone secondaries, superior vena caval obstruction or haemoptysis. Combinations of radiotherapy and platinum-based chemotherapy provide the best palliation for patients with good performance status and non-resectable disease.
Multi-agent chemotherapy is indicated for small cell carcinoma. There is a small survival benefit from palliative combination chemotherapy in non-small-cell lung cancer. Trials are currently underway to determine whether there is a role for induction chemotherapy in patients with locally advanced non-small-cell lung cancer. Responders, if downstaged, can be offered surgical resection with a view to long-term survival. This management strategy remains controversial and should currently only be offered in the context of a properly conducted randomised clinical trial.
The mediastinum is a midline space between the pleural cavities. It is divided into the superior, anterior, middle and posterior compartments. Mediastinal tumours may be primary or secondary in origin. Secondary neoplasms most often result from lymphatic spread to mediastinal lymph nodes. Common primary sites are lung, oesophagus, larynx, thyroid and stomach. A classification of primary mediastinal tumours is given in Classification of primary mediastinal tumours.
Approximately half are asymptomatic and have no abnormal findings on examination. They are discovered by chance on a plain chest X-ray. Lesions in the young and those with symptoms are more likely to be malignant.
Thoracic symptoms result from compression of adjacent structures and include pain (back or chest), shortness of breath, cough or dysphagia. Systemic symptoms may be fever, malaise, weight loss and night sweats. Local findings include cervical lymphadenopathy, facial and/or arm swelling and tracheal shift. General findings may be testicular masses, hepatosplenomegaly and muscle weakness.
Neurogenic tumours are the most common mediastinal tumours and are found almost exclusively in the posterior mediastinum. About 10% are malignant and this feature is more frequent in children. All nerve types may be affected (Classification of primary mediastinal tumours).
Germ cell tumours are the most common anterior mediastinal tumours and are more common in the young. Types include teratoma, seminoma and nonseminomatous. Tumour markers may be elevated in non-seminomatous types and can be used to monitor the response to therapy.
Mediastinal lymphoma is usually associated with widespread disease and is seldom the only site (5%). Ninety per cent are either lymphoblastic (Hodgkin's) or diffuse large cell (non-Hodgkin's) in type.
Thymoma is more common in adults than children. About 30% of patients have myasthenia gravis and about 15% of patients with myasthenia gravis develop thymoma. The differentiation between benign (encapsulated) and malignant (invasive) thymoma can be difficult.
Investigations are summarised in Investigation of mediastinal tumours. In some instances, the combination of clinical features and findings on imaging allow a precise diagnosis. A patient with myasthenia gravis and an anterior mediastinal mass will most likely have a thymoma. The site of the lesion will determine the type of biopsy required.
Options in management include simple observation and follow-up, aspiration, surgical resection, radiotherapy, chemotherapy and combinations of surgical resection, radiotherapy and chemotherapy. A summary of the approach to management of the common primary mediastinal tumours is given in .
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