Lung cancer is the second most common cancer and is the leading cause of death due to cancer, according to the U.S. Centers for Disease Control and Prevention (CDC). Lung cancer is divided into two broad categories, small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), based upon histopathological evaluation. Cancer staging is important in describing a tumor and for determining a course of treatment and estimating prognosis. Non-small cell lung cancer is staged according to the TNM system which classifies tumors into four stages. Small-cell lung cancer is staged differently and is designated as either limited or extensive.
Stage I
Stage I is the least advanced stage of lung cancer with the highest prognosis. In this stage, the tumor is small, localized to one location in a single lung, and does not involve any lymph nodes, which are small immune system filtering organs found throughout the body. Stage I is subdivided into stage IA and IB, primarily based upon the size of the tumor. IA tumors are up to 3cm in size while IB tumors are larger, between 3 to 5cm.
Stage II
In stage II lung cancer, the primary tumor is still confined to one lung, but may or may not have spread to nearby lymph nodes. Like the first stage, it is further divided into stages 2A and 2B based upon size and spread to nearby organs. A stage 2A tumor is 5 to 7cm in size, localized to a single location in the lung and has not spread to any nearby organs. Stage 2B tumors are still 5 to 7cm in size, but cancer cells from the primary tumor have spread to nearby lymph nodes or other areas such as the chest wall or diaphragm.
Stage III
Stage III lung cancer tumors are generally larger in size and have spread beyond the lung to more distant lymph nodes or other organs in the chest region. Stage IIIA tumors are larger than 7cm in size or have spread beyond nearby lymph nodes to more distant ones. Stage IIIB tumors can be any size, but the spread of the cancer is more extensive. Lymph nodes on the opposite side of the chest of the primary tumor are involved or chest structures such as the heart, trachea, diaphragm or esophagus contain cancer cells.
Stage IV
The most advanced stage of lung cancer with the lowest prognosis is stage IV. The tumor is no longer localized to one lung or region of the body, but has spread (metastasized) throughout the body. Tumors are found in both lungs in stage IV or metastasis to distant organs has occurred. The brain or bones are the most common sites of metastasis for primary tumors of the lung.
Limited and Extensive
Small-cell lung cancer (SCLC) is designated as either limited or extensive because metastasis has generally already occurred and more detailed classification is unnecessary. Limited SCLC is generally confined to one lung and may involve lymph nodes on the same side of the chest. Extensive SCLC is more advanced in which the primary tumor of the lung has spread to distant organs throughout the body.
