Cancer is an uncontrollable growth of cells, often called tumors, anywhere within the body. Malignant tumors are likely to cause death if left untreated. The abnormal cells are classified by naming the tissue in which the abnormal cells originated. The four most common types are sarcoma, carcinoma, leukemia, and lymphoma. They affect bone or muscle tissue, epithelial tissue, the blood and bone marrow, and the lymphatic system, respectively.
Sarcoma is a type of cancer that forms from tissue such as bone or muscle, and these malignant tumors can be found developing in the arms or legs. Harmful tumors that grow on smooth muscles are called leiomyosarcomas. These tumors can be found behind the abdominal cavity and in internal organs composed of muscle. Sarcoma is more common in the elderly than young adults and children.
Malignancies that originate from epithelial cells, including skin cancer, are referred to as carcinomas. Epithelial tissue is found lining the surfaces and cavities of organs, including the surface of the body itself. Skin cancer is the most common form of human cancer. Over one million new cases occur annually around the world, including the least dangerous form, basal cell carcinoma, and the most dangerous type, melanoma. Carcinomas can develop in any epithelial tissue, including the lungs, where malignancies often take the form of carcinomas.
Leukemia develops in the bone marrow and blood cells. In patients with leukemia, the bone marrow makes abnormal white blood cells, which crowd the healthy blood cells. Experts classify leukemia as either acute or chronic. Children and adults exposed to radiation have an increased chance of developing this type of malignancy.
Cancer of the lymphatic system is called lymphoma. The lymphatic system is made up of a network of vessels that carry lymph fluid, which contains white blood cells called lymphocytes that work to attack infectious agents. Malignant tumors within the lymphatic system surround tissues by invading their space. As a result, oxygen and nutrients are cut off, and the tissue dies.
The spread of a malignancy beyond the initial site is referred to as metastasis. Cancer cells spread from one area of the body by entering into the bloodstream or lymphatic system. Malignancies can move from one area and create a new tumor in a different organ. Imaging tests detect whether the cancer has spread to other areas. Experts are able to identify the malignant tumors according to the markers or antigens found in the cancer cells.