Lung Cancer Diagnosis - Lung Cancer Diagnosis

Diagnosis

Doctors explore the possibility of lung cancer when a person, especially a smoker, has a persistent or worsening cough or other lung symptoms (such as shortness of breath or coughed-up sputum tinged with blood). Usually, the first test is a chest x-ray, which can detect most lung tumors, although it may miss small ones. Sometimes a shadow detected on a chest x-ray done for other reasons (such as before surgery) provides doctors with the first clue, although such a shadow is not proof of cancer.

A computed tomography (CT) scan may be done next. CT scans can show characteristic patterns that help doctors make the diagnosis. They also can show small tumors that are not visible on chest x-rays and reveal whether the lymph nodes inside the chest are enlarged. Newer techniques, such as positron emission tomography (PET—see Symptoms and Diagnosis of Lung Disorders: Chest Imaging) and a certain type of CT called helical (spiral) CT, are improving the ability to detect small cancers. Oncologists frequently use PET-CT scanners, which combine the PET and CT technology in one machine, to evaluate patients with suspected cancer. Magnetic resonance imaging (MRI) can also be used if the CT or PET-CT scans do not give doctors sufficient information.

A microscopic examination of lung tissue from the area that may be cancerous is usually needed to confirm the diagnosis. In rare cases, a sample of coughed-up sputum can provide enough material for an examination (called sputum cytology). Almost always, doctors need to obtain a sample of tissue directly from the tumor. One common way to obtain the tissue sample is with bronchoscopy. The person's airway is directly observed and samples of the tumor can be obtained (see Symptoms and Diagnosis of Lung Disorders: Bronchoscopy). If the cancer is too far away from the major airways to be reached with a bronchoscope, doctors can usually obtain a specimen by inserting a needle through the skin while using CT for guidance. This procedure is called a needle biopsy (see Symptoms and Diagnosis of Lung Disorders: Needle Biopsy of the Pleura or Lung). Sometimes, a specimen can only be obtained by a surgical procedure called a thoracotomy (see Symptoms and Diagnosis of Lung Disorders: Thoracotomy). Doctors may also perform a mediastinoscopy, in which they take and examine samples of enlarged lymph nodes (a biopsy) from the center of the chest to determine if inflammation or cancer is responsible for the enlargement.

Once cancer has been identified under the microscope, doctors usually do tests to determine whether it has spread. A PET-CT scan and head imaging (brain CT or MRI) may be done to determine if lung cancer has spread, especially to the liver, adrenal glands, or brain. If a PET-CT is not available, CT scans of the chest, abdomen, and pelvis and a bone scan are done. A bone scan may show that cancer has spread to the bones. Because small cell lung cancer can spread to the bone marrow, doctors sometimes also do a bone marrow biopsy.

Cancers are categorized on how large the tumor is, whether it has spread to nearby lymph nodes, and whether it has spread to distant organs. The different categories are used to determine the stage of the cancer (see Symptoms and Diagnosis of Cancer: Diagnostic Tests and Staging). The stage of a cancer suggests the most appropriate treatment and enables doctors to estimate the person's prognosis.