Lung cancer. Coloured chest X-ray with a bronchial carcinoma (red, upper right) in the upper lobe of the patient's left lung. The heart (orange) lies between the two lungs. The shoulder bones (across top) and rib bones (enclosing the chest) are also seen. A carcinoma is a malignant growth (cancer) of epithelial tissue, a tissue that lines the skin and internal organs like the lungs. This carcinoma is growing and spreading along the inside of the branching lung airways (bronchioles). It is caused by atmospheric pollution and primarily by smoking, causing coughing and breathlessness. Radiotherapy and surgery are suitable for some lung cancers.