The stages of non-small cell lung cancer include T1, T2, T3, T4, N1, N2, N3 and M1, according to the American Cancer Society. The letters indicate what is being affected by the cancer, while the numbers indicate its severity.
The indicator "T" in a stage refers to how large the primary tumor is and how deeply it has invaded the lung tissue, explains the American Cancer Society. A T1 stage tumor is less than 1 1/4 inches in diameter, does not involve the main bronchial tubes and does not reach the membranes surrounding the lungs. T4 is the most severe stage and indicates the tumor has grown large enough to severely affect the breathing passages and surrounding organs such as the heart or the major blood vessels around it. T4 also indicates there are at least two tumor nodules in the same lung.
The indicator "N" in a stage refers to the involvement of lymph nodes, according to the American Cancer Society. An N1 tumor has spread only to lymph nodes very near the primary tumor, while an N3 tumor has spread to lymph nodes as far away as the collarbone. Cancer at the M1 stage has metastasized to other organs of the body.