Lung cancer is a cancer that originates in the lungs. More than 220,000 Americans are diagnosed with lung cancer each year. And lung cancer causes more than 157,000 deaths annually, making it the leading cause of cancer death in men and women. Those most at risk are people aged 50 or older, who have a history of cigarette, cigar, or pipe smoking. However, people who have never smoked can also develop the disease due to past lung infections, environmental factors, and genetic predisposition.
There are two main types of lung cancer: small cell (SCLC) and non-small cell (NSCLC). Treatment options and prognosis depend on the type and stage of cancer. Lung cancer often goes undetected in the early stages, since symptoms don’t usually present themselves until the advanced stages of the disease. Symptoms include a persistent cough, coughing up blood, chest pain, recurring chest infections, and hoarseness.
Cancer occurs when cells in the body that normally grow, divide, and die undergo a mutation that causes them to grow rapidly and uncontrollably. Lung cancer forms when cancer cells invade and destroy healthy cells in the tissue of the lungs and in the lining of the air passages. It can take several years to develop, beginning as precancerous changes to the lungs that do not cause symptoms or show up on an x-ray. Eventually, cancer cells accumulate to form a tumor. As the tumor grows, it impedes the ability of the lungs to function properly, causing breathing problems. Cancerous cells can break away from the original tumor, travel through the bloodstream, and form tumors in other parts of the body. This process is called metastasis.
Types of Lung Cancer
There are two main types of lung cancer—small cell and non-small cell. The names refer to how the cells appear to pathologists under a microscope. Each type and stage of lung cancer warrants unique treatment options.
Small cell lung cancer accounts for 15-20% of all lung cancers. The cells are oval-shaped and, as the name suggests, smaller than most other cancer cells. Starting in the bronchi (the air tubes that lead to the lungs) or in lung tissue, it is fast-growing and produces large tumors that can travel through the blood and spread quickly throughout the body. Small cell lung cancer mainly affects heavy or lifetime smokers.
There are three subtypes of small cell lung cancer: oat cell carcinoma, mixed small cell/large cell carcinoma, and combined small cell carcinoma. Oat cell cancer is the most common type of small cell lung cancer.
Non-small cell lung cancer makes up the majority of lung cancer cases (about 80%). The cancer cells are larger, and it is slower growing than small cell lung cancer. NSCLC consists of three sub-types:
- Squamous cell carcinoma (or epidermoid carcinoma) accounts for 25%-30% of all lung cancer. It begins in the cells that line the air passages and, if not treated, may spread to the lymph nodes, bones, adrenal glands, liver, and brain. It is the most common type of lung cancer in men and is heavily linked to smoking.
- Adenocarcinoma makes up about 40% of all lung cancer. It forms in the mucus-producing (outer) part of the lungs. It develops slowly and is the most common type of lung cancer in women and nonsmokers.
- Large-cell (undifferentiated) carcinoma includes all non-small cell lung cancer that can’t be classified as squamous or adenocarcinoma (about 10-15%). It sometimes forms near the surface, in the outer edges of the lungs, and grows rapidly.
Written by: the Healthline Editorial Team
Medically reviewed by Gregory Cosby