Doctors describe nonsmall cell lung cancer based on the size of the lung tumor and whether cancer has spread to the lymph nodes or other tissues:

Occult stage: Lung cancer cells are found in sputum or in a sample of water collected during bronchoscopy, but a tumor cannot be seen in the lung.

Stage 0: Cancer cells are found only in the innermost lining of the lung. The tumor has not grown through this lining. A Stage 0 tumor is also called carcinoma in situ. The tumor is not an invasive cancer.

Stage IA: The lung tumor is an invasive cancer. It has grown through the innermost lining of the lung into deeper lung tissue. The tumor is no more than 3 centimeters across (less than 1 ¼ inches). It is surrounded by normal tissue and the tumor does not invade the bronchus. Cancer cells are not found in nearby lymph nodes.

Stage IB: The tumor is larger or has grown deeper, but cancer cells are not found in nearby lymph nodes. The lung tumor is one of the following (see the picture of the main bronchus and pleura):

• The tumor is more than 3 centimeters across.
• It has grown into the main bronchus.
• It has grown through the lung into the pleura.

Stage IIA: The lung tumor is no more than 3 centimeters across. Cancer cells are found in nearby lymph nodes.

Stage IIB: The tumor is one of the following:

• Cancer cells are not found in nearby lymph nodes, but the tumor has invaded the chest wall, diaphragm, pleura, main bronchus, or tissue that surrounds the heart.

• Cancer cells are found in nearby lymph nodes, and one of the following:
• The tumor is more than 3 centimeters across.
• It has grown into the main bronchus.
• It has grown through the lung into the pleura.

Stage IIIA: The tumor may be any size. Cancer cells are found in the lymph nodes near the lungs and bronchi, and in the lymph nodes between the lungs but on the same side of the chest as the lung tumor.

Stage IIIB: The tumor may be any size. Cancer cells are found on the opposite side of the chest from the lung tumor or in the neck. The tumor may have invaded nearby organs, such as the heart, esophagus, or trachea. More than one malignant growth may be found within the same lobe of the lung. The doctor may find cancer cells in the pleural fluid.

Stage IV: Malignant growths may be found in more than one lobe of the same lung or in the other lung. Or cancer cells may be found in other parts of the body, such as the brain, adrenal gland, liver, or bone.

Educational information provided by The National Cancer Institute (NCI) Internet site.