Description
Lung cancer is now the leading cause of cancer deaths among men and women. The peak incidence of lung cancer occurs between ages 55 and 65 years.
At the time of diagnosis, only about 20 percent of all lung cancer patients will have local disease, while about 25 percent will have disease that has spread to regional lymph nodes and about 55 percent will have distant metastatic cancer.
Cigarette smoking is the most important cause of lung cancer in both men and women in the US.
Primary carcinoma of the lung is a major health problem with a generally grim prognosis. However, an orderly approach to diagnosis, staging, and treatment based on knowledge of the clinical behavior of lung cancer allows selection of the best therapy for either potential cure or optimal palliation [reduce the severity] of individual patients. This approach is often multidisciplinary, involving the interaction of internists, chest physicians, medical, radiation, and surgical oncologists, pathologists, and supportive care personnel.
Cancers that originate in the skin, glands, or lining of internal organs (such as the lungs), are known as carcinomas. There are four main types of carcinomas of the lungs which can be further categorized as non-small or small cell cancers. The four major cell types make up 95 percent of all primary lung neoplasms.
Small Cell Carcinoma
Also called oat cell carcinoma because the cells are shaped like grains of oats, this form of lung cancer accounts for 20 percent to 25 percent of lung cancers. It is the most aggressive form, and the most likely to have spread by the time of diagnosis.
Non-small Cell
(Squamous or Epidermoid). These arise from the flat, scaly cells that line the air passages. It is the most common form of lung cancer, accounting for 35 percent of all lung cancers. Squamous cell carcinoma tends to be centrally located.
Adenocarcinoma
This type of tumor can begin in the mucous membrane of both smaller or larger bronchi. It accounts for about 30 percent of all lung cancers. It can also be caused by smoking, but to a lesser degree than other forms of lung cancer.
Large Cell Carcinoma
This is the least common form of lung cancer, accounting for 15 percent of all cases. It usually develops in the bronchus and is characterized by large, round cells.
Normally, the body cells divide and reproduce in an orderly manner, so that we replace worn-out tissue and repair any injuries. Sometimes, however, cells divide without control and form masses known as tumors.
Tumors may invade or destroy normal tissue, interfere with body functions, and require removal by surgery. Benign tumors do not spread to other parts of the body. Cancerous or malignant tumors do.
By a process known as metastasis, cells break away from the original malignant tumor and spread through the lymph and blood systems to form more malignant tumors elsewhere in the body. This spread can occur rapidly or over a period of years. Lung cancers tend to spread more quickly than most types of cancer.
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