Updated: November 22, 2017
An abnormality in the cell of the body results in cancer. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when new cells are needed. An uncontrolled division and proliferation of cells results when disruption of this system of checks and balances on cell growth happens that eventually forms a mass known as a tumor.
Tumors can be benign or malignant. Benign tumors usually can be removed and do not spread to other parts of the body where as malignant tumors often grow aggressively locally where they start. Tumor cells also can enter into the bloodstream or lymphatic system and then spread to other sites in the body. This process of spread is termed metastasis.
Since lung cancer tends to spread very early after it forms, it is a very life-threatening cancer and one of the most difficult cancers to treat. Lung cancer can spread to any organ in the body particularly the adrenal glands, liver, brain, and bones.
The lungs bring oxygen into the body when breathing in and send carbon dioxide out of the body when breathing out.
Lung cancers, also known as bronchogenic carcinomas because they arise from the bronchi within the lungs. Lung cancer can be divided into two major types based on the appearance of lung cancer cells under the microscope. These two types of cancers grow and spread in different ways and the treatment decisions are based on which major type of lung cancer you have. The two general types of lung cancer include:
Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer. SCLC are the most aggressive and rapidly growing of all lung cancers. SCLC metastasize rapidly to many sites within the body and are most often discovered after they have spread extensively.
NSCLC are the most common lung cancers and can be divided into several main types that are named based upon the type of cells found in the tumor.
These type of tumor arises in the outer or peripheral areas of the lungs.While adenocarcinomas are associated with smoking like other lung cancers, this type is observed as well in nonsmokers who develop lung cancer.
This is a subtype of adenocarcinoma that frequently develops at multiple sites in the lungs and spreads along the preexisting alveolar walls.
These are also known as epidermoid carcinomas or squamous cell cancers arise most frequently in the central chest area in the bronchi.
Sometimes referred to as undifferentiated carcinomas, are the least common type of NSCLC.
A combination of different types of NSCLC also are seen sometimes.
These tumors are referred to as lung neuroendocrine tumors. They are generally small about 3 to 4 cm or less when diagnosed and occur most commonly in people under 40 years of age. These are not related to cigarette smoking and can metastasize. A small proportion of these tumors secrete hormone-like substances that may cause specific symptoms related to the hormone being produced. Carcinoids generally grow and spread more slowly than bronchogenic cancers, and can be detected in early stage.
Cancers of supporting lung tissue such as smooth muscle, blood vessels, or cells involved in the immune response can rarely occur in the lung.
Metastatic cancers from other primary tumors in the body are often found in the lung. Tumors from anywhere in the body may spread to the lungs either through the bloodstream, lymphatic system, or directly from nearby organs. These are most often multiple, scattered throughout the lung, and concentrated in the peripheral rather than central areas of the lung.