About Cancer: A General Overview
What is Cancer ? Cancer refers to cells that grow out-of-control and invade other tissues. Cells become cancerous due to the accumulation of defects, or mutations, in their DNA.
What causes Cancer? Certain inherited genetic defects and infections can increase the risk of cancer. Environmental factors (for example, air pollution) and poor lifestyle choices -- such as smoking and heavy alcohol use -- can also damage DNA and lead to cancer.
Usually, cells are able to detect and repair DNA damage. If a cell is severely damaged and cannot repair itself it undergoes so-called programmed cell death (apoptosis). Cancer occurs when damaged cells grow, divide, and spread abnormally instead of self-destructing as they should.
Cancer Classifications and Staging Cancer can occur anywhere in the body. Broadly, cancers are classified as either solid (for example, breast, lung, or prostate cancers) or liquid (blood cancers).
Cancer is further classified according to the tissue in which it arises.
• Carcinomas occur in epithelial (lining) tissues in the body. They comprise 80% to 90% of all cancers. Most breast, lung, colon, skin, and prostate cancers are carcinomas. • Sarcomas occur in connective tissue like the bones, cartilage, fat, blood vessels, and muscles. • Myelomas are cancers that occur in plasma cells in the bone marrow. • Leukemia are blood cancers of the bone marrow. • Lymphomas are cancers of the immune system cells. • Mixed cancers arise from more than one type of tissue.
What does “stage” mean when referring to a cancer diagnosis?
• Stage 0: This refers to cancer that is “in situ,” meaning that cancerous cells are confined to their site of origin. This type of cancer has not spread and is not invading other tissues. • Stage I – Stage III: These higher stages of cancer correspond to larger tumors and/or greater extent of disease. Cancers in these stages may have spread beyond the site of origin to invade regional lymph nodes, tissues, or organs. • Stage IV: This type of cancer has spread to distant lymph nodes, tissues, or organs in the body far away from the site of origin. Stages of Cancer
Stage 0 Stage I Stage II Stage III Stage IV Carinoma in Localized Early locally Late locally Metastasized situ- Early advanced advanced form
What is metastasis? What does it mean when cancer is “metastatic”? Metastasis occurs when cancer cells break free from a tumor and travel to and invade other tissues in the body via the lymphatic system and the bloodstream.
Cancer cells from the original -- or primary -- tumor can travel to other sites such as the lungs, bones, liver, brain, and other areas. These metastatic tumors are “secondary cancers” because they arise from the primary tumor.
NOTE: Metastatic cancer retains the name of the primary cancer. For example, bladder cancer that metastasizes to the liver is not liver cancer. It is called metastatic bladder cancer. Metastasis is significant because it helps determine the staging and treatment of cancer. Some types of metastatic cancer are curable, but many are not.
Benign vs. Malignant Tumors
Benign (non-cancer) tumor cells Malignant (cancer) cells invade grow only locally and cannot neighboring tissues, enter blood vessels, spread by invasion or metastasis. and metastasize to different sites
SOURCE: Medicine Net - http://www.medicinenet.com/cancer_101_pictures_slideshow/article.htm