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Cancerous tissues (malignancies) can be divided into those of the blood and blood-forming tissues (leukemias and lymphomas) and "solid" tumors, often termed cancer. Cancers can be carcinomas or sarcomas.
Leukemias and lymphomas are cancers of the blood and blood-forming tissues. Rather than forming a lump, they may remain as separate cancerous cells. Thus, they often harm the body by crowding out normal blood cells in the bone marrow and bloodstream, so that normal functioning cells are gradually replaced by cancerous blood cells.
Carcinomas are cancers of epithelial cells, which are cells that cover the surface of the body, produce hormones, and make up glands. Examples of carcinomas are cancer of the skin, lung, colon, stomach, breast, prostate, and thyroid gland. Typically, carcinomas occur more often in older than in younger people.
Sarcomas are cancers of mesodermal cells, which are the cells that form muscles and connective tissue. Examples of sarcomas are leiomyosarcoma (cancer of smooth muscle that is found in the wall of digestive organs) and osteosarcoma (bone cancer). Typically, sarcomas occur more often in younger than in older people.
Last full review/revision February 2003
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