Definition of Lung Cancer:
Cancer is the uncontrolled growth and spread of abnormal cells anywhere in the body. However, cancer is not just one disease; it is actually an umbrella term for at least 100 different but related diseases.
Cancer is not caused by injuries, nor is it contagious. It cannot be passed from one person to another like a cold or flu virus.
Cancer is almost always caused by a combination of factors that interact in ways that are not yet fully understood. Cancer forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.
Cancer begins in cells, the building blocks that make up all tissues and organs of the body, including the lungs.
Normal cells in the lungs and other parts of the body grow and divide to form new cells as they are needed. When normal cells grow old or get damaged, they die, and new cells take their place.
Sometimes, this process goes wrong. New cells form when the body doesn’t need them, and old or damaged cells don’t die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.
Lung cancer cells can spread by breaking away from a lung tumor. They can travel through blood vessels or lymph vessels to reach other parts of the body. After spreading, cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.
When lung cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary (original) tumor. For example, if lung cancer spreads to the bones, the cancer cells in the bones are actually lung cancer cells. The disease is metastatic lung cancer, not bone cancer. For that reason, it is treated as lung cancer, not bone cancer.
Small cell: The cells of small cell lung cancer look small under a microscope. About 1 of every 8 people with lung cancer has small cell lung cancer.
The types of small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look when viewed under a microscope:
Non-small cell: The cells of non-small cell lung cancer are larger than the cells of small cell lung cancer. Most (about 7 of every 8) people diagnosed with lung cancer have non-small cell lung cancer. It doesn’t grow and spread as fast as small cell lung cancer, and it’s treated differently.
The types of non-small cell lung cancer are named for the kinds of cells found in the cancer and how the cells look under a microscope:
•Squamous cell carcinoma: Cancer that begins in squamous cells, which are thin, flat cells that look like fish scales. This is also called epidermoid carcinoma.
•Large cell carcinoma: Cancer that may begin in several types of large cells.
•Adenocarcinoma: Cancer that begins in the cells that line the alveoli and make substances such as mucus.
Doctors describe the stages of non-small cell lung cancer using the Roman numerals I, II, III, and IV. Stage I is early-stage cancer, and Stage IV is advanced cancer that has spread to other parts of the body, such as the bones.
Lung Cancer is also discussed in terms of Localized, Regional and Distant"
Stage 0 Lung Tumor
Abnormal cells are found only in the innermost lining of the lung. The tumor has not grown through this lining. A Stage 0 tumor is also called carcinoma in situ. It is not an invasive cancer.
Stage I Lung Cancer
The lung tumor is an invasive cancer. It has grown through the innermost lining of the lung into deeper lung tissue. The tumor is surrounded by normal tissue, and it doesn't invade nearby tissues, such as the chest wall.
Stage II Lung Cancer
The lung tumor is smaller than 7 centimeters across, and cancer cells are found in nearby lymph nodes or cancer cells are not found in nearby lymph nodes. The lung tumor is more than 5 centimeters across, or it invades nearby tissues, such as the chest wall, diaphragm, pleura, main bronchus, or tissue that surrounds the heart. More than one malignant tumor may be found within the same lobe of the lung.
Stage III Lung Cancer
The tumor may be any size. More than one malignant tumor may be found within the lung. Cancer cells may be found in lymph nodes on either side of the chest or the neck. The tumor may have invaded nearby organs, such as the heart, esophagus, or trachea.
Stage IV Lung Cancer
Malignant tumors are found in both lungs or the lung cancer has spread to other parts of the body, such as the brain, bones, liver, or adrenal glands or cancer cells are found in fluid between the two layers of pleura.