About 80% of people who have lung cancer have non-small-cell lung cancer. NSCLC usually spreads more slowly than small-cell lung cancers. Both cancers affect the lungs and have similar symptoms, but they’re treated differently. Types There are three main categories of NSCLC: Adenocarcinoma: This is the most common type. It usually spreads more slowly than others, and it’s more likely to be found earlier. It’s often linked to a history of smoking, but it is also the most common type of lung cancer seen in nonsmokers. It starts in the cells that make mucus, and it’s usually found in the outer parts of your lung.