TUMORS
Tumors can be divided into two groups,
benign (noncancerous), and
malignant (cancerous). Benign tumors do not
spread to other parts of the body, but they may cause damage by local growth and pressure on other structures, producing serious complications such as airway obstruction and bleeding. In addition, they may rarely become
malignant. Examples of benign tumors are hamartomas, lipomas, fibromas, and dermoid cysts. Adenomas, once classified as benign, are now considered low-grade malignancies.
Cancers of the respiratory system can involve the nose, throat, tongue, vocal cords, wind pipe (trachea), and lungs. The most common form is lung
Cancer, which frequently develops from the cells lining the airways of the lungs. The incidence of lung cancer increased rapidly after about 1940, and this form of cancer is now the leading cause of cancer death in both men and women. One major cause of lung cancer is cigarette smoking. Exposure to environmental pollution, materials such as asbestos and chromium, and radioactive substances such as radon increase the probability of developing this form of cancer.
There are a number of other malignant tumors, unrelated to smoking, which may originate in the lung, including lymphomas (which arise in the lymph nodes related to the lungs), Hodgkin's disease, and sarcomas. In addition, the lungs are often the location of cancers that have metastasized, or spread, from other parts of the body, such as the breast.