Pulmonary neoplasms

Carcinoma of the bronchus is the most common malignancy in men and the second most common (after carcinoma of the breast) in women. A number of neoplasms affects the airways and suspicion of carcinoma of the bronchus should prompt thorough investigation to make the diagnosis at an early and therefore treatable stage.

Benign tumours

Benign tumours of the lung are uncommon and account for less than 15 per cent of solitary lesions seen on chest radiographs. They are usually an incidental finding on a chest - radiograph done for some other reason, but symptoms, when present, depend on the site of the lesion. A peripheral tumour may produce little in the way of symptoms, whereas a centrally placed tumour may present with haemoptysis and signs of bronchial obstruction at a relatively early stage. A tumour is likely to be benign if it has not increased in size on chest radiograph for more than 2 years or has some degree of calcification. However, a tissue diagnosis is advisable as a noncalcified solitary lesion may be a primary carcinoma.

Most benign nodules are granulomas (tuberculosis or histoplasmosis), which give the appearance of a high-density lesion on CT. Low-density appearances are suspicious and the nodule should be removed by excision biopsy. Less than SO per cent of solitary nodules are benign, underlining the importance of accurate diagnosis.

The most common benign tumour is the pulmonary hamartoma which is really a developmental abnormality containing mesothelial and endothelial elements. They may be lobulated and, although unlikely to undergo malignant transformation, they may be multicentric. Diagnosis (and definitive treatment) is achieved by excising the lesion.

   Epithelial tumours

  Epithelial tumours of the airways are a particularly trouble­some problem. The airways become infected with a papil­loma virus at birth and small stalk-like papillomas develop, initially in the larynx and then down into the major airways. Regular endoscopic follow-up is required following bronchoscopic resection, because recurrence is common and malignant change may occur.

Fibroma

Fibroma is the most common mesodermal tumour and tends to occur in the bronchi rather than the trachea. Fibromas are often pedunculated and therefore easily removed at bron­choscopy.

Hamartoma

Hamartoma is a disorganised mass of tissue within the lung substance containing respiratory structures. It is the result of a developmental abnormality and malignant change is rare. Any of the mesodermal elements of the lung may form a mesodermal tumour (chondroma, lipoma, leiomyoma). Deposits of amyloid may give similar radiographic appearances of a nodule (pseudotumour).

Bronchial adenomas

Bronchial adenomas are mainly carcinoid tumours derived from the neuroendocrine cells of bronchial glands. Most (80 per cent) are found in the major bronchi and are characteristically slow growing and highly vascular. Occasionally these tumours secrete hormones adenocorticotrophic hormone (ACTH), melanocyte-stimulating hormone or insulin]. This may be the first presentation but usually there are recurrent chest infections, persistent cough, haemoptysis and occasionally chest pain. Carcinoid tumours belong to a class of tumours that are benign at one end of the scale, to those that are locally aggressive and to the highly malignant oat cell tumour at the other end of the scale. Surgical excision is the most appropriate treatment and regular follow-up is advised.

Malignant tumours

Carcinoma of the bronchus, as stated earlier, is the most common malignancy in men and the second most common in women (following carcinoma of the breast), resulting in over 30000 deaths per year in the UK (Fig. 47.11). There is only a 20 per cent 1-year survival for all cases after diagnosis and surgery represents the best chance of prolonged survival.

Accurate diagnosis and staging of the tumour are vital if surgery is to be considered. The real incidence of carcinoma of the bronchus earlier in the twentieth century was probably masked by the presence of tuberculosis. Once a cure for tuberculosis became available, the importance of carcinoma of the lung became apparent. Cigarette smoking is undoubtedly one of the major risk factors for developing bronchial carcinoma. To a lesser extent, atmospheric pollution and certain occupations (radioactive ore and chromium mining) also contribute to the problem. In the UK, the mortality from lung cancer for individuals smoking more than 40 cigarettes per day is over 210/100 000. This compares to a mortality of less than 4/100 000 in nonsmokers. Regular smoking causes characteristic changes in the bronchial epithelium from hyperplasia through squamous metaplasia to preinvasive carcinoma in situ. These changes are to some extent reversible if smoking is stopped.

Histological types

Many bronchial and lung tumours have more than one cell type, and the behaviour and prognosis depend largely on the dominant cell type seen. There are several histological types which have an important bearing on prognosis and response to treatment.

Squamous cell carcinoma (SCC) accounts for the majority (over 60 per cent) of lung cancers. It is uncommon in non­smokers and tends to be centrally placed. There is a tendency to cavitate and metastasise outside the thoracic cavity.

Adenocarcinoma is less common than SCC (15 per cent) in the UK but the incidence can vary in different countries. It is more common in females and nonsmokers, and tends to be sited in the periphery of the lung. Adenocarcinoma often metastasise widely to the liver, brain and adrenals. The typical histological appearance is that of gland formation and the only worthwhile treatment, if feasible, is surgical excision (Fig. 47.12). It is important to exclude secondary adeno­carcinoma from other sites such as colon, breast and ovary.

Small cell carcinoma metastasises widely early in its course and is therefore rarely amenable to surgical resection. If discovered early then surgical removal has led to increased survival, but palliative chemotherapy and radiotherapy are the most appropriate treatment. These tumours are often associated with ectopic hormone production and paraneoplastic syndromes. The 5-year survival is less than S per cent, even with treatment.

Alveolar cell carcinoma arises in the distal airways. Resec­tion of a solitary nodule is associated with a good prognosis but the occurrence of a multicentric pneumonic type of alveolar cell carcinoma is associated with a poor prognosis.

Clinical features

Clinical features of lung carcinoma depend on:

  the site of the lesion;

  invasion of neighbouring structures;

the extent of metastases.

Common symptoms include a persistent cough, weight loss, dyspnoea and nonspecific chest pain. Haemoptysis occurs in less than SO per cent of patients presenting for the first time. Severe localised pain suggests chest wall invasion with the infiltration of an intercostal nerve. Invasion of the apical area may involve the brachial plexus leading to Pancoast’s syndrome. Dyspnoea may come from loss of func­tioning lung tissue, lymphatic invasion or the development of a large pleural effusion. Clubbing and hypertrophic pul­monary osteoarthropathy are sometimes seen, particularly with squamous cell lesions. These features may resolve with excision of the primary lesion. The presence of blood in a pleural effusion suggests that the pleura is invaded. Invasion of the mediastinum may result in hoarseness (due to recurrent laryngeal nerve involvement), dysphagia (due to involvement of, or extrinsic pressure on, the oesophagus) and superior vena caval obstruction. Hormonal secretion by a tumour will have predictable pathological and physiological effects depending on the nature of the hormone. Small cell carcinoma is associated with the development of myopathies including the Eaton—Lambert syndrome, which is similar to myaesthenia gravis although the weakness tends to improve with repeated movement.

Diagnosis and staging

There are three keys to diagnosis:

  detection of the primary lesion;

  tissue diagnosis;

  assessment of spread (Table 47.2)

Detection of the primary lesion. Chest radiography. The principal investigation in detecting pulmonary pathology is a good-quality posteroanterior chest radiograph with an additional lateral view. The radiographic appearance will vary according to the site of the lesion and its effects (pleural effusion, lobar collapse, raised hemidiaphragm) (Fig. 47.13).

  Computerised tomography (CT). This is more sensitive and reproducible than tomography, and has become almost routine in the assessment of these patients. The questions that the surgeon wants answered are (1) is the lesion resectable and (2) are the mediastinal lymph nodes involved? These two questions determine the prognosis (Fig. 47.14). Unfortunately, CT cannot always provide the answers. Lymph nodes more than 2 cm in diameter are likely to be involved in the disease (70 per cent) but those smaller than this (1—2 cm) may or may not be involved. Mediastinal lymph nodes of less than 1 cm in the longest axis are very unlikely to be involved. Visualisation of the liver by CT is a useful means of excluding metastases. Involvement of the mediastinal lymph nodes is usually regarded as a contraindication to surgery, but this view is continually debated. Enthusiasts of resection still seek to cure lung cancer by more extensive resection in N2 disease. Resection is only justified in the presence of metastases if there is chronic debilitating sepsis from a cavitating tumour or uncontrolled haemoptysis.

Sputum cytology may reveal malignant cells but the false-negative rate is high, particularly in poorly differentiated lesions.

Bronchoscopy is used to visualise the bronchial tree and is useful in a number of ways (Table 47.3).

Flexible bronchoscopy may be performed with the patient awake and the oropharynx anaesthetised with topical ligno­caine (Fig. 47.15). The bronchoscope is passed into the nose and through the vocal folds under direct vision. As the scope is flexible its tip can be directed into the segmental bronchi with ease. Tissue and sputum samples may be obtained for diagnostic purposes. There is a greater range of movement with this instrument but the biopsies are relatively small and the suction facility may not be adequate. Nearly 40 per cent of biopsy diagnoses require modification following resection.

Rigid bronchoscopy. The rigid bronchoscope requires a general anaesthetic in most cases. However, it is ideal for therapeutic manoeuvres such as removal of foreign bodies, aspiration of blood and thick secretions, and intraluminal surgery (laser resection or stent placement). This instrument, introduced under general anaesthesia, allows visualisation and generous biopsy of the lesion (Fig. 47.15). The surgeon and the anaesthetist share control of the airway. The view is improved by using muscarinic premedication and paralysing agents. Continuous ECG and pulse oximetry monitoring are now mandatory. The operator stands behind the patient and lifts the maxilla by the upper teeth with the middle and forefinger of the left hand. The bronchoscope rests on the left thumb as it is introduced over the tongue in the midline. As the bronchoscope is passed under direct vision into the oropharynx, the neck is extended and the bronchoscope is lowered and advanced to visualise the larynx. Turning the instrument through 90degree will help to negotiate the vocal cords. Care must be taken not to trap the lips or tongue between the teeth and the bronchoscope and the fulcrum should be the left thumb and not the teeth. The tracheal rings and the carina should be easily seen. Advancing the bronchoscope into the main bronchus reveals the orifices of the more peripheral bronchi. Operability is determined by the proximity of a lesion to the carina and whether or not the carina is widened (indicating inoperability from subcarinal lymph node involvement). If the bronchoscopy is for diagnosis rather than preoperative assessment, a biopsy may be taken. This should be done when the anaesthetist is satisfied that the anaesthetic can be quickly reversed. The biopsy is taken and a check made for bleeding. The anaesthetic is reversed and the patient turned on the side. This will allow drainage and easy expectoration of any blood or secretions.

Biopsy is hazardous under the following conditions:

    bleeding disorders;

   •  systemic anticoagulation;

   •  pulmonary hypertension.

  Complications are rare in experienced hands but include bleeding, pneumothorax, laryngospasm and arrhythmia.

Bronchoscopy may not visualise the lesion unless it is in the main airways, and is inadequate for staging operable disease. More invasive techniques of biopsy of intrathoracic lesions are often necessary to confirm diagnosis, stage disease and plan treatment. The options range from percutaneous needle biopsy under radiological control to open lung biopsy (see below).

Needle biopsy. A thin needle passed into a lesion through the chest wall under local anaesthesia gives a good yield of malignant cells. It is best reserved for large or peripheral lesions and is performed under radiological CT control. Pneumothoraces are common (30 per cent) but rarely require intercostal tube drainage. Seeding in the biopsy track and haemorrhage are also reported complications. This proce­dure is also used in the diagnosis of life-threatening pneumonia where other attempts to establish a diagnosis have failed. The contraindications are similar to those of bronchoscopy but include those with poor respiratory reserve in whom even a small pneumothorax would be fatal.

The more invasive techniques of thoracoscopy, mediastinoscopy, mediastinotomy and open lung biopsy, are aimed at establishing a tissue diagnosis and assessing the degree of spread (staging) which determines resectability. Mediastinoscopy or mediastinotomy is advisable on all patients who have enlarged lymph nodes (>1 cm) on CT of the mediastinum to avoid futile thoracotomy without hope of cure. Smaller nodes are not likely to be involved and thoracotomy may be done based on the benefit of doubt. Whatever staging procedure is used, there will inevitably be a small rate (<S per cent) of nonresective thoracotomies.

Mediastinoscopy. This procedure is performed under gen­eral anaesthesia with the patient supine and the neck extend­ed (Fig. 47.16). A transverse incision is made 2 cm above the sternal notch and deepened until the strap muscles are reached. These are retracted laterally and the thyroid isthmus superiorly to reveal the pretracheal fascia. Careful blunt dissection in this plane allows direct palpation of the paratracheal and subcarinal nodes. A mediastinoscope may be introduced for direct visualisation and biopsy. Care must be taken to avoid damage to the brachiocephalic vessels anteriorly.

Mediastinotomy. An incision is made through the second intercostal space to gain access to some of the mediastinal lymph nodes on the affected side (Figs 47.17 and 47.18). Damage to the internal mammary artery and great vessels must be avoided. Biopsy of the mediastinal lymph nodes is possible and the medial extension of tumour can be assessed, so this technique has important application in the staging of lung cancer.

Great caution should be used in the presence of superior vena caval obstruction and previous exploration is a relative contraindication. Complications include pneumothorax and haemorrhage. These techniques may also be used in the diagnosis of other mediastinal conditions, including:

  lymphoma;

  anterior mediastinal tumours;

thymoma;

 sarcoid or any other cause of lymphadenopathy.

 Thoracoscopy. A thoracoscope may be introduced through a small stab incision and a peripheral lesion biopsied. This requires general anaesthesia and double-lumen intubation. The technique has more application in the diagnosis of suspected metastatic disease and malignant pleural effusion (see Pleura).

Open lung biopsy. This requires a thoracotomy and is rarely performed to diagnose carcinoma. The site of the incision is dictated by the site of the lesion.

Treatment of lung cancer

Only 10 per cent of patients have potentially curable lesions on presentation, so careful investigation is required to determine which patients are operable and will benefit from a major thoracic resection. The internationally agreed staging system [tumour, node, metastasis (TNM)] gives some prognostic information on the natural history of the disease but it assumes that lung cancer behaves and spreads in a progressive manner by local invasion of the lymph nodes and then into the bloodstream. Tumours graded T2, N1, M0 or less have a better prognosis when treated surgically. This means that the tumour must be staged as accurately as possible before resection (Table 47.4). Unfortunately, most lung cancers are beyond curative treatment at the time of presentation. However, palliation is a skilled process from which patients may benefit in terms of quality of life and disease-free survival. If preoperative investigations suggest that a lesion is localised and resectable then surgery should be undertaken. A number of factors including general fitness of the patient and the lung function tests determines the nature of treatment. Many patients are smokers and elective physiotherapy before the operation may be worthwhile.

 Surgical management

 The principle of surgery is to remove all cancer (the primary and the regional lymph nodes) but to conserve as much lung as possible. This is usually done by lobectomy but there is evidence that small peripheral lesions have as good an outcome if subjected to segmentectomy or simple wedge excision. A double-lumen tube for separate control of the lungs is used to facilitate dissection. It should be remembered, however, that techniques of one-lung anaesthesia were developed by anaesthetists to protect the nonoperated lung and to retain their control (Fig. 47.19).

Following exploration of the fissure, the lobar artery is isolated and ligated. The vein is then divided and oversewn leaving the affected bronchus, which is divided so as not to leave a stump. The divided bronchus is oversewn or stapled according to preference (Fig. 47.20).

At the completion of the operation, the remaining lung is reinflated. Air leak is common and usually settles within a number of days. Intercostal drains are inserted to lie basally and apically. The patient is extubated in the recovery area once ventilation is deemed adequate.

Pneumonectomy is removal of the whole lung. This is a major undertaking and has a high mortality rate (5—10 per cent). The surgeon must be satisfied that the patient is fit enough to tolerate this procedure from the preoperative work-up. This procedure is reserved for either centrally placed tumours involving the main bronchus or those that straddle the fissure. At thoracotomy, an inspection of the lung and direct palpation of the mass will determine resectability and lymph node spread. Fixation of the tumour to the aorta, heart or oesophagus implies irresectability. Involvement of the mediastinal lymph chain is associated with a poor prognosis. In all, 5—10 per cent of thoracotomies are exploratory only with no resection. The objective is to keep this to a minimum but extensive conservation would deny the patient a chance of cure.

Pneumonectomy, if performed, involves isolation of the main pulmonary artery after the initial exploration. An occlusive clamp is placed across the artery and, if this is tolerated, the resection proceeds. The artery is divided and oversewn. The pulmonary veins are then isolated and clamped. They too are divided and oversewn. This leaves the main bronchus which is divided so that no blind stump remains (Fig. 47.21). The technique of stump closure is important if a bronchopleural fistula is to be avoided. The tissues are carefully handled and the stump is closed with good apposition of the sides. Topical antibiotics may be used to prevent infection. The chest cavity is irrigated with warm saline to remove any blood clots or debris. Some saline is left in the hemithorax to cover the bronchial stump. The anaesthetist manually ventilates after the clamp is removed from the tube serving the affected side. The inflation pressures are gradually increased until the surgeon is satisfied that there is no leak present (by the absence of bubbles in the saline). Haemostasis is vital because there is a large space left after pneumonectomy. Drainage is a matter of preference. Some prefer to insert drains and unclamp them for 1 minute every hour until the drainage ceases; others prefer not to drain. The critical point is that no suction should be applied as there is now a sealed space with the mobile mediastinum on one side of it. The air in the pneumonectomy space is gradually absorbed and the fluid level within the space rises (Fig. 47.22).

Thoracoscopic lung resection. Minimally invasive surgery has become fashionable in recent years in all forms of surgery. The thoracoscope has been used for many years but its use was limited mainly to performing biopsies. The instru­ment had a limited view and was uncomfortable to use for any length of time. All this has changed since the advent of video-assisted thoracoscopy (Fig. 47.23). The surgeon’s hands are freed because the camera is attached to the thoracoscope which can be operated by an assistant; and the image is displayed on a television screen. The surgeon is able to manipulate instruments with both hands to perform an impressive variety of procedures. Pneumonectomy, lobec­tomy and empyema drainage are all possible, but thoracoscopic procedures for common, more minor problems is the area providing clear justification for this technique. Lung biopsy and the treatment of recurrent pneumothorax are the most frequent indications for this technique of operation. The principal advantage is that a large incision is not required and therefore less postoperative pain and a more rapid recovery should result. The scope of thoracoscopic surgery is increasing with the modern trend of less invasive surgery. Thoracoscopic lobectomy is now a feasible and reproducible procedure although the long-term results remain unproven. The thoracoscope is used in staging lung and oesophageal malignancy and in sympathectomy. Port access coronary artery surgery will be discussed in Chapter 48.

 Complications of lung resection

 Bleeding should be avoidable by use of careful surgical technique but may be very severe in the presence of dense adhesions.

Respiratory infection. Many of these patients are ex smokers so basal collapse and hypoxaemia are common post­operatively.

Persistent air leak. Chest drains placed at the time of surgery should deal with this problem, but occasionally the air leak becomes chronic and the remaining lung does not expand. Re thoracotomy may then be necessary to seal the leak.

Bronchopleural fistula. Following pneumonectomy, the space left behind is initially filled with air. This is slowly reabsorbed and the space fills with tissue fluid. The fluid level rises until the air is finally reabsorbed. Dehiscence of the bronchial stump leads to the development of a bronchopleural fistula and the tissue fluid (which is almost inevitably infected) is expectorated in large quantities. This is a catastrophic complication with high morbidity and mortality. The patient is laid flat with the affected side down (to prevent infected fluid from entering the remaining lung) while arrangements are made to site a pleural drain. Bronchopleural fistulas are unlikely to resolve with conservative treatment and therefore some operative strategy must be tried. There is a number of ways of sealing the fistula, from tissue glue down the rigid bronchoscope to thoracotomy and a muscle flap to cover the bronchial stump. Bronchoscopic sealing with tissue glue may be successful but is difficult. Resuturing the bronchial stump may lead to healing and the thoracotomy will allow evacuation and thorough irrigation of the pneumonectomy space. Closure is more successful if viable tissue can be brought over the bronchial stump. This is achieved by dissecting a pedicle of intercostal muscle off the chest wall leaving its artery and vein intact and suturing it over the repair. Omentum is an alternative source of pedicled tissue. If closure is not possible or the patient will not tolerate closure, then a fenestration procedure may be performed to allow drainage of the fluid, usually including rib resection. Suturing the skin to the pleural surface to form a Clagett window provides chronic management in desperate circumstances.

Hypoxaemia. Poor oxygenation, as a result of pre-existing lung damage, pulmonary oedema from overenthusiastic crystalloid replacement, atelectasis and bronchopneumonia, may occur. Treatment is aimed at the underlying cause but great care must be taken in pneumonectomy patients who are very susceptible to hypoxaemia.

Survival

 Carcinoma of the bronchus generally has a low survival rate after diagnosis (Table 47.5).

  Important factors in determining prognosis are the histological type of tumour, the spread (stage) and the general condition of the patient. The 5-year survival rate is less than 2 per cent if no treatment is offered at the time of diagnosis and ipsilateral lymph nodes are involved. Those with mediastinal lymph nodes discovered and removed at thoracotomy have a better prognosis (15—30 per cent 5-year survival). Early detection and surgical resection offer the best hope for cure.