Lung cancer tissue. Illustration of a section through lung tissue showing normal cells and cancer cells. At upper right are columnar epithelial cells with cilia (yellow), with basal cells (blue) at left. At centre are flattened squamous epithelial cells. At bottom are cancer cells, shown proliferating and infiltrating and invading surrounding tissues. Cancer cells divide in an uncontrolled fashion, into undifferentiated irregular shapes, and migrate to invade other tissues. Treatment is with surgery if the cancer is still localised, and chemotherapy and radiotherapy if it has spread.