Some lung cancers produce abnormally high blood levels of certain hormones or substances such as calcium. If a person shows such evidence and no other cause is apparent, a doctor should consider lung cancer.
Lung cancer, which originates in the lungs, can also spread to other parts of the body, such as distant bones, the liver, adrenal glands, or the brain. It may be first discovered in a distant location, but is still called lung cancer if there is evidence it started there.
Once lung cancer begins to cause symptoms, it is usually visible on an X-ray. Occasionally, lung cancer that has not yet begun to cause symptoms is spotted on a chest X-ray taken for another purpose. A CT scan of the chest may be ordered for a more detailed exam.
Though exams of mucus or lung fluid may reveal fully developed cancer cells, diagnosis of lung cancer is usually confirmed through a lung biopsy. With the patient lightly anesthetized, the doctor guides a thin, lighted tube through the nose and down the air passages to the site of the tumor, where a tiny tissue sample can be removed. This is called a bronchoscopy and the scope is called a bronchoscope. This is useful for tumors near the center of the lung.
If the biopsy confirms lung cancer, other tests will determine the type of cancer and how far it has spread. Nearby lymph nodes can be tested for cancer cells with a procedure called a mediastinoscopy, while imaging techniques such as CT scans, PET scans, bone scans, and either an MRI or a CT scan of the brain can detect cancer elsewhere in the body.
If fluid is present in the lining of the lung, removal of the fluid with a needle (called a thoracentesis) may help diagnose cancer as well as improve breathing symptoms. If the fluid tests negative for cancer cells -- which occurs about 60% of the time -- then a procedure known as a video-assisted thoracoscopic surgery (or VATS) may be performed to examine the lining of the lung for tumors and to perform a biopsy.