1. Cancer: A disease in which abnormal cells multiply out of control, spread into surrounding tissues and other body parts, and disrupt normal functioning of one or more organs.

2. (4)Classes of Cancer 1.Cancer in the immune system organs are lymphomas. 2.Cancers of blood forming organs are leukemias. 3.Cancers of the glands and body linings are carcinomas. 4.Cancers of connecting tissue, including bones, ligaments, and muscles are sarcomas.

3. Lymphomas Lymphomas are broadly divided into Hodgkin's Lymphoma and Non-Hodgkin's Lymphoma Both diseases are lymphomas, a type of cancer that originates in a subset of white blood cells called lymphocytes. The difference between Hodgkin's and non- Hodgkin's is in the specific lymphocytes involved.

4. Leukemia What is Leukemia? Leukemia is a cancer of the blood cells. There are several types of leukemia and these are classified by how quickly they progress and what cell they affect. In order to understand how leukemia affects the cells, it is helpful to first understand what normal blood cells do. White blood cells are the body's infection fighting cells. Red blood cells give blood it's red color, but more importantly, carry oxygen from the lungs to the rest of the body and return carbon dioxide to the lungs as waste. Platelets (help the body form blood clots to control bleeding. In addition to these three cell types, the blood also contains a fluid called plasma.

5. Carcinomas These cancers are classified into six categories: Adrenocortical carcinoma, which arises from the adrenal cortex, the outside layer of the adrenal gland. The cells in the adrenal cortex make hormones that help the body work properly, such as steroids and hormones important for sexual development and maturation. When cells in the adrenal cortex become cancerous, they may make too much of one or more hormones, which can cause symptoms such as high blood pressure, weakening of the bones, or diabetes. If male or female hormones are affected, the body may go through changes such as a deepening of the voice, growing hair on the face, swelling of the sex organs, or swelling of the breasts. Thyroid carcinoma, which arises from the thyroid, a gland located in the neck that manufactures hormones that affect heart rate, body temperature, energy level, and also control the level of calcium in the blood. Nasopharyngeal carcinoma, which affects the nose and pharynx. Malignant melanoma, a cancer of the skin. Skin carcinoma other than melanoma. Other and unspecified carcinomas.

6. How Cancer Develops 1.Exposure to carcinogen 2.Possible speeding up of cancer formation by a promoter. 3.Out of control multiplication