linguistic:paraphrasing, information:highlighting, structural:scholar_edition, stylistic:style_transfer, stylistic:tone
Staging

Lung cancer staging is an assessment of the degree of spread of the cancer from its original source. It is one of the factors affecting both the prognosis and the treatment of lung cancer.

SCLC is typically staged with a relatively simple system: limited stage or extensive stage. Around a third of people are diagnosed at the limited stage, meaning cancer is confined to one side of the chest, within the scope of a single radiotherapy field. The other two thirds are diagnosed at the "extensive stage", with cancer spread to both sides of the chest, or to other parts of the body.

NSCLC – and sometimes SCLC – is typically staged with the American Joint Committee on Cancer 's Tumor, Node, Metastasis (TNM) staging system. The size and extent of the tumor (T), spread to regional lymph nodes (N), and distant metastases (M) are scored individually, and combined to form stage groups.

Relatively small tumors are designated T1, which are subdivided by size: tumors ≤ 1 centimeter (cm) across are T1a; 1–2 cm T1b; 2–3 cm T1c. Tumors up to 5 cm across, or those that have spread to the visceral pleura (tissue covering the lung) or main bronchi, are designated T2. T2a designates 3–4 cm tumors; T2b 4–5 cm tumors. T3 tumors are up to 7 cm across, have multiple nodules in the same lobe of the lung, or invade the chest wall, diaphragm (or the nerve that controls it), or area around the heart. Tumors that are larger than 7 cm, have nodules spread in different lobes of a lung, or invade the mediastinum (center of the chest cavity), heart, largest blood vessels that supply the heart, trachea, esophagus, or spine are designated T4. Lymph node staging depends on the extent of local spread: with the cancer metastasized to no lymph nodes (N0), pulmonary or hilar nodes (along the bronchi) on the same side as the tumor (N1), mediastinal or subcarinal lymph nodes (in the middle of the lungs, N2), or lymph nodes on the opposite side of the lung from the tumor (N3). Metastases are staged as no metastases (M0), nearby metastases (M1a; the space around the lung or the heart, or the opposite lung), a single distant metastasis (M1b), or multiple metastases (M1c).

These T, N, and M scores are combined to designate a stage grouping for the cancer. Cancer limited to smaller tumors is designated stage I. Disease with larger tumors or spread to the nearest lymph nodes is stage II. Cancer with the largest tumors or extensive lymph node spread is stage III. Cancer that has metastasized is stage IV. Each stage is further subdivided based on the combination of T, N, and M scores.