Of the lethal diseases asbestos exposure can cause, mesothelioma, which is a cancer of the pleura, or membrane surrounding the lungs, is probably the most commonly known. Yet asbestos can also cause lung cancer (bronchogenic carcinoma or adenocarcinoma) – a cancer of the lung tissue itself.
Diagnosing any asbestos-related disease is challenging: symptoms develop gradually, are non-specific, and can mimic other conditions or diseases. Even when the physician is aware of asbestos exposure, or the patient has a history of asbestosis, which leads to an asbestos cancer in approximately 1 out of 7 cases, the diagnosis must rule out other possibilities.
Complete Blood Count
A thorough and accurate medical history is always the first step, documenting medical conditions, work history, and family medical history, and taking into consideration cultural and environmental factors. A general physical exam follows, including listening with a stethoscope for labored breathing, wheezing, or fluid in the lungs. Sometimes laboratory tests, such as a complete blood count may be ordered.
When a physician suspects a lung condition, he will usually prescribe a pulmonary function test and chest x-ray. The pulmonary function test, which measures lung function, shows if the patient’s breathing ability is what would be considered normal for a person of the patient’s age, physical condition, and ethnic background. The chest x-ray detects lung abnormalities, including pleural thickening (scarring), effusions (excessive liquid), and lesions (fibrotic growth).
Once the presence of any of these lung abnormalities is established, any of the following tests may be required to determine if asbestos lung cancer is present, how far it has progressed, and what treatments are indicated. Often, several are used in conjunction to provide a complete picture.
Sputum cytology, which analyzes the patient’s phlegm, may be requested. As this test is very straight forward and deceptively simple, its importance in cancer diagnosis may be overlooked; sputum cytology can detect cancer cells in their earliest stages.
A Computed Tomography Scan (CT scan or CAT scan) is an x-ray that rotates around the patient, producing a three-dimensional, cross-sectional image. Unlike the flat-image x-ray, an accurate assessment of the size of the abnormality can be made and differences in tissue density can be seen. You will have an injection of dye before the scan to help show up abnormalities.
Positron emission tomography (PET) scans help identify tumors, and, in suspected lung cancer, are most often used to complement information from CT scans. The patient receives an injection of radioactive sugar molecules, which causes tissue that uses glucose to appear brighter on the scan. Because tumors use more glucose than normal tissue, tumors are readily identifiable with this test, although PET scans cannot distinguish between malignant and benign tumors.
Ultrasound uses high-frequency sound waves to “see” the parameters of a tumor or other abnormality. It is most often used in conjunction with endoscopic or other biopsy procedures (see below).
While imaging tests like CT scans, PET scans and ultrasound provide invaluable information, lung cancer, asbestos-related or otherwise, cannot be diagnosed without analysis of the abnormal tissue or tumor. This requires a biopsy, or physical removal of tissue for examination. Physicians usually prefer to make use of the least invasive methods first, resorting to more invasive if a diagnosis cannot be reached.
Needle aspiration biopsies use syringe needles to suck tissue and/or fluid from the patient’s lung or pleura. If a conclusive diagnosis cannot be made from the material obtained through the use of a fine needle, or if a larger tissue sample is needed, the physician may opt for a core needle biopsy, which yields a cylinder of tissue for examination.
When the purpose of needle aspiration is to collect a sample of the fluid that surrounds the lungs, where cancer cells can also be found, the procedure is called thoracentesis.
If the physician needs larger samples of tissue, he may order a vacuum-assisted biopsy, in which suction is used to pull tissue through a hollow needle. Vacuum-assisted biopsies are particularly useful in cases where samples are needed from more than one location, as they can be gathered by this method without having to insert the needle more than once.
Often, these needle-type biopsies are performed with the visual guidance of imaging technology, such as ultrasound, x-rays, CT scan, or fluoroscopy (live x-ray images transmitted to a screen).
In a bronchoscopy (an endoscopic procedure), a thin, flexible tube (a bronchoscope) terminating with a light and camera is passed through the mouth, down the windpipe and into the lungs. A bronchoscopy can be used simply to view the upper airways and lungs, but can also obtain tissue for biopsy.
Saline solution is introduced through the tube, flushing the lungs and collecting lung cells, fluids and other materials present. Sometimes, tiny instruments like brushes or forceps are pushed through the tube to retrieve tissue samples. If imaging tests or a previous bronchoscopy shows larger abnormalities or indicates a possible tumor, the bronchoscope used may be rigid and larger, allowing larger tissue samples to be gathered.
Similar endoscopic biopsies may be performed, like a thoracoscopy (sometimes called VATS, or video-assisted thorasoscopy), entering the chest or lungs through small incisions in the chest, or a mediastinoscopy, which examines the center of the chest (mediastinum) and nearby lymph nodes.
As a last step in final diagnosis when needle or endoscopic biopsies show the presence of cancer cells, the physician will order a surgical biopsy. Depending on the size of the suspicious tissue, an incisional biopsy involves removing a piece of the suspicious tissue. The surgeon will perform an excisional biopsy when the lump is small enough to be removed completely at one time. In both cases, the tissue is examined to determine if it is benign or cancerous.
In some cases, a thoracotomy will be ordered. Considered major surgery, a throacotomy requires a surgeon to open the chest and examine the lung directly, removing tissue for testing and analysis.
Without the information provided by proper testing, asbestos lung cancer cannot be diagnosed. Only a biopsy and analysis of the tissue affected can conclusively determine if the disease is present, how far it has progressed, and provide informed treatment options.