The Approach To The Patient With A Lung Mass

History and Physical Exam

The patient who presents with the chest x-ray finding of lung mass must be evaluated to quickly and accurately determine the etiology of the lesion and establish a treatment plan. The history and physical examination are of prime importance. The patient is asked about symptoms of cough, sputum production, chest pain, shortness of breath and weight loss. Hemoptysis is an important finding. A previous history of tuberculosis should be elicited. Physical examination should include cardiopulmonary examination and a search for nodes in the axilla, supraclavicular regions and neck, as well as a general physical examination. Given a negative general history and physical examination without signs of another primary lesion, the chance of a solitary lung lesion being a metastasis from another organ is less than 5% and it is almost certainly a new primary in the lung.

The presence of tuberculosis should never be underestimated since it comes in many disguises. As with appendicitis for the abdomen, tuberculosis as a rule should never be less than second on a list of differential diagnoses for lung pathology. On a broader perspective, lung lesions in general can be categorized into tumors, infectious etiologies, trauma, congenital lesions or idiopathic problems. This will be described in more detail in relation to the solitary pulmonary nodule.

Inspection of the pulmonary mass on the chest x-ray should be carefully done. There are some clues that could give insight into the pathology of the lesion. Generally, tuberculosis is found in the apices of the lung although it can be found in any location in the lung. Cavitary lesions associated with carcinoma are generally squamous cell carcinomas. Squamous cell carcinomas and small cell carcinomas are usually, but not universally, centrally located whereas large cell tumors and adenocarcinomas are in general more peripherally located. The presence of pop

corn calcification, lamellar calcification or target calcification in general implies benign disease such as a granuloma, although carcinoma cannot be excluded.

A general laboratory work-up of the patient with a lung mass includes CBC and electrolytes. The fundamental work-up of lung mass then includes sputum cytology, CT scan of the chest and flexible fiberoptic bronchoscopy. These three tests should be included in the preoperative evaluation of all lung masses. CT scan is useful for a number of reasons, not only to further define the location and extent of the lung lesion, but also to identify any synchronous lesions that may have been missed on the chest x-ray. Most importantly the CT evaluates for mediastinal adenopathy, the presence of which may require investigation. The use of CT scanning as a modality for staging of lung carcinoma is controversial. In general, in the United States the standard of care for staging of lung carcinoma is by CT scan. Mediastinal nodes greater than 1.0 cm require further evaluation. Node enlargement may represent either reactive inflammation or may represent involvement with carcinoma. Further assessment of these nodes is done either by mediastinoscopy, anterior mediastinotomy (Chamberlain procedure), or by video-thoracoscopic methods. Conversely, nodes less than 1.0 cm are generally considered negative; however both the sensitivity and specificity of CT scanning in staging of lung cancer is only 85%. In other words, the chance of an enlarged node on CT scanning indeed being positive for carcinoma is only 85%, whereas the chance of a node less than 1.0 cm being negative for carcinoma is again also 85%. In other countries such as Canada, mediastinal lymph node sampling by mediastinoscopy or mediastinotomy are considered routine.

The diagnosis of the lesion may be achieved by sputum cytology or by bronchoscopy with biopsy of the lesion or bronchial brushings, and/or bronchial washings. If the lesion still cannot be diagnosed, then several alternatives are available. One is to perform a fine needle aspiration of the lung lesion. The problem with this technique is that there is a 10% chance of a pneumothorax, and that a malignant lesion may result in a negative or nondiagnostic needle aspiration. This occurs approximately 15% of the time, and thus although a positive fine needle aspiration may be helpful, a negative fine needle aspiration may be harmful if it is incorrect. Therefore some advocate going straight to thoracotomy when the above work-up has not determined the etiology of the lesion, rather than performing fine needle aspiration. The one lesion where a fine needle aspiration is extremely helpful is in the case of a superior sulcus tumor (i.e. Pancoast's tumor). Management of this tumor involves preoperative radiation therapy followed by surgical resection of the chest wall en bloc with the tumor. Thus, positive aspiration cytology will prevent a diagnostic thoracotomy prior to radiotherapy. Other instances where fine needle aspiration may be very helpful is where there are suspicions for small cell carcinoma, lymphoma, or infectious etiologies (e.g., tuberclosis).

After all these preoperative diagnostic and staging procedures have been done, surgical resection may be considered. The primary questions to be answered are:

1) Is the patient a suitable candidate for thoracotomy and major pulmonary resection?

2) Is the lesion itself surgically resectable in terms of the local lesion itself and in terms of mediastinal node involvement?

Whether the patient himself is a suitable candidate for resection depends on the history and physical examination, arterial blood gas and pulmonary functions tests, and evaluation of the patient's overall condition. If he is too cachectic and malnourished to undergo major thoracotomy, then this is an important consideration. Are there other co-morbid conditions such as synchronous cancer, coronary artery disease or peripheral vascular disease, or other problems that may make pulmonary resection dangerous?

The arterial blood gas is of prime importance in determining if patient is a candidate for surgery. The PaCO2 is the most important factor in this determination. Generally, if the resting pCO2 is greater than 45 mmHg operation is precluded because by definition, the patient is not ventilating adequately and will not have enough pulmonary reserve for a major lung resection. Another simple test which is a good assessment of pulmonary reserve is to take the patient up a flight of stairs and observe how the patient is able to tolerate this. If this is well tolerated, he generally has enough reserve to tolerate a major lung resection.

Pulmonary function tests are invaluable in assessing a patient for lung resection. The FEV-1 is the most important determinant in this. It is generally thought that a predicted postoperative FEV-1 of less than 0.8 liters precludes resection. This rule may be tempered by various circumstances. For example, a sedentary, old lady may do well with an FEV-1 of 0.8, whereas a younger man, otherwise active and healthy, may do poorly if his predicted postop FEV-1 is less than 1 liter. Although clinical judgment is important, the value of 0.8 liters is generally considered a boundary which should not be crossed. There are various ways to determine the postoperative FEV-1. For example, if a patient has a preoperative FEV-1 of 2.0 liters, a pneumonectomy will presumably reduce his FEV-1 by half with the postop FEV-1 being 1.0 liters. Using these determinants and knowledge of the segmental anatomy of the lungs, one will be able to determine what the resultant FEV-1 will be after resection of a lobe or segment.

To determine this, it is important to understand the segmental anatomy of the lungs. On the right side, there are three segments in the upper lobe, two segments in the middle lobe and five segments in the lower lobe. This makes a total of ten segments in the right lung. On the left side, there are four segments in the upper lobe (two segments in the upper lobe proper and two segments in the lingula), and there are four segments in the lower lobe making a total of eight segments. Overall, approximately 55% of the total lung function is contributed from the right lung and 45% of the total lung function is contributed from the left lung. One can thus assess whether to do a resection based on postoperative function predicted by the number of segments resected. For example, if one does a right upper lobectomy in a patient with an FEV-1 of 1.1 what will be the predicted FEV-1? In a right upper lobectomy, three segments are removed. There are a total of 18 segments in the lung on the left and right sides combined. Fifteen remaining segments divided by 18 equals 0.83; 0.83 times 1.1 equals 0.91 liters for a predicted postop FEV-1. Therefore, it would be considered acceptable to do the lobec-

tomy if other patient factors including arterial blood gas are acceptable.

It is important to note that anytime a patient's postoperative FEV-1 will be marginal, a quantitative ventilation-perfusion scan is very useful. This will help determine which portions of the lung are nonfunctional and therefore do not contribute to overall lung function. For example, if a patient has a right upper lobe lesion and a marginal FEV-1, a ventilation-perfusion scan may be helpful because if there is little ventilation and little perfusion to the right upper lobe then this can be considered a nonfunctioning lobe and therefore resection will not hinder and, in fact, may help the patient's overall FEV-1. If the perfusion data and the ventilation data conflict as to the lung function, the perfusion data are always used.

In the example given above, if a ventilation perfusion scan is done in this patient with a preoperative FEV-1 of 1.1 which reveals that 35% of the perfusion is going to the right upper lobe, then it can be presumed that 100-35 = 65% of remaining lung function will be present postoperatively; 65% x 1.1 = 0.72 liters for the predicted postoperative FEV-1; this precludes right upper lobectomy.

Another important point is that for any lung lesion, one must ask the following question before entering the operating room: Can the patient tolerate a pneumonectomy if this is needed? For example, if the patient has a right lower lobe lesion and is found to have a level 11 interlobar lymph node, then many thoracic surgeons will perform a pneumonectomy because the interlobar node is impinging on the right upper lobe as well. The patient may be able to tolerate a lobectomy but not a pneumonectomy based on the preoperative pulmonary functions, and therefore it is always important to keep in mind before doing the operation whether or not a pneumonectomy can be performed in any given patient.

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