Lung cancer is the number one cancer killer in the U.S.  However, when a lesion is found in the lungs, doctors often wait to do a biopsy because diagnostic testing is invasive and the risks of the tests are very high. 

Lung cancer remains the top cause of cancer death in the U.S, with an estimated 174,500 new cases and 163,000 deaths expected this year.  According to the National Cancer Institute (NCI), the overall 5-year survival rate for those with lung cancer is 15% with nearly 90 percent of patients dying within two years.  The survival rate is low because lung cancer is often not detected until it has reached an advanced stage.  In its early stages, lung cancer is usually asymptomatic.  There are relatively few nerve endings in the lung so a small tumor doesn't cause pain or other symptoms such as cough or shortness of breath. It's only when it gets larger that it starts to cause symptoms. 

The NCI suggests that catching lung cancer early - when surgery is a treatment option - improves survival substantially, and 70 percent of patients who are diagnosed early may survive at least five years.  Unfortunately, early detection is often a matter of luck, when a nodule or mass is discovered because a test is being done for a different reason.  Even then, proceeding to a definitive diagnosis is problematic as doctors balance the risks versus the usefulness of tests.  Ultimately, tissue needs to be obtained to confirm the diagnosis of lung cancer, usually meaning an invasive procedure must be used. 
 
Nodules can be present in the lungs for a variety of reasons, cancer being only one of them.  Noncancerous lung nodules usually cause no symptoms and require no treatment.  In fact, multiple nodules are frequently found in smokers, but for every hundred smokers found with one or more nodules, only two or three smokers will have cancer.  The challenge is to separate the bad from the benign.  

Doctors use a wide range of diagnostic tools to diagnose lung cancer.

• Medical history.  To assess risk factors for developing lung cancer.
• Physical exam.  To look for symptoms of lung disease and swollen lymph nodes.
• Complete blood count.  To check for abnormal values of blood cells that may be indicative of a problem, though not necessarily cancer.
• Certain tests to determine electrolyte and liver function. To determine if cancer is present and has spread to other tissue or body organs.
• Sputum cytology.  To evaluate the type of any abnormal cells present in mucus.  This is the most risk-free and inexpensive tissue diagnostic procedure, but its value is limited since tumor cells will not always be present in sputum even if a cancer is present
• Chest X-ray.  To look for a nodule or a change in a nodule from an earlier x-ray. Nodules that grow need to be aggressively evaluated.
• Computerized tomography (CT) scan. To examine for both metastatic and primary tumors. CT scans are more sensitive than standard chest x-rays in the detection of lung nodules.
• Thoracentesis.  To take a sample of fluid, if some has accumulated between the lungs and chest wall, and evaluate abnormal cells.
• Bronchoscopy. To take a biopsy of cells.  A tumor in the central areas of the lung or arising from the larger airways is accessible to sampling using this technique.
• Transthoracic needle biopsy.  To retrieve cells for diagnosis.  Needle biopsies are particularly useful when the lung tumor is peripherally located in the lung and not accessible to sampling by bronchoscopy.
• Thoracoscopy.  To take a biopsy of lung tissue through several small incisions between the ribs.
• Major surgical procedures.  To determine a definitive diagnosis if all other methods fail and in some cases to simultaneously remove as much tumor as possible. 

Non-surgical invasive biopsy procedures do carry risk.  Up to 25 percent of patients may suffer a collapsed lung as a result of a needle biopsy and half of those may need to have a chest tube inserted to re-expand the lung. The risks of bronchoscopy are lower (3 to 5 percent) than a needle biopsy and include bleeding, infection, collapse of the lung and risks of the sedative medications used to complete the procedure.

Risks of lung surgery (wedge resection, lobectomy and pneumonectomy) follow those of any major surgery. These include reactions to anesthesia, bleeding, infection, and problems restoring breathing.  Pneumonia and blood clots are of particular concern in lung surgery.