About 15% of all lung cancer cases are small cell lung cancer. Small cell lung cancer is slightly more common in men than women.
Almost all cases of SCLC are due to cigarette smoking. SCLC is rare in those who have never smoked.
SCLC is the most aggressive form of lung cancer. It usually starts in the breathing tubes (bronchi) in the center of the chest. Although the cancer cells are small, they grow very quickly and create large tumors. These tumors often spread rapidly (metastasize) to other parts of the body, including the brain, liver, and bone.