Lung cancer. Coloured scanning electron micrograph (SEM) of a section through muscle tissue from the lung, showing adenocarcinoma (cancer) cells (beige with red cell nuclei) and a mitochondrion (purple). Adenocarcinoma is a non-small cell lung cancer that is more commonly found in women and non-smokers, and it is the most common type of lung cancer for people under 45. It accounts for approximately 50% of all non-small cell lung cancers and begins in the outer sections of the lung (although it can occur as central lesions) which can make it difficult to detect in the early stages of the disease. Magnification: x9000, when printed 15 centimetres wide.