WHAT IS CANCER? The word "cancer" actually refers to a group of over a hundred diseases. All forms are caused by the growth of abnormal cells within the body. DNA Cancer cells are called "malignant" because they continue to grow and spread in a way that destroys normal parts of the body. Destructive masses called malignant tumors are formed. These tumors damage organs and may eventually spread (metastasize) to distant parts of the body. Cancers can originate in almost any cell of the body. Different types of cancer respond to different forms of treatment. Microscope Thus, it is crucial that cancer be diagnosed correctly. It is also important to determine the "grade" of a malignant tumor. This predicts the behavior or aggressiveness of the cancer, which is used to select the most effective form of treatment. Low-grade tumors grow and metastasize (spread) relatively slowly. High-grade tumors, in contrast, grow rapidly-- causing more destruction of normal tissue-- and tend to metastasize early.

WHAT ARE THE DIFFERENT TYPES OF CANCER? With over a hundred different forms, cancers are divided into broad categories based on the cell type from which they started. Each distinct cell line in the human body, when malignant, gives rise to a different kind of cancer. Cancers are grouped into the following categories: carcinomas leukemias and lymphomas melanomas sarcomas. Carcinomas (i.e. lung cancer, breast cancer, colon cancer, and prostate cancer, among others) are by far the most common group and account for over 90 percent of all cancer cases. Carcinomas arise from the cells that comprise the inner linings of organs and the glands of the body. The most common ones are "adenocarcinomas" (from glands) and "squamous cell carcinomas" (from skin cells and the cells that line inner surfaces of the body). Different kinds of carcinomas respond to different types of treatment. For any patient researching his or her disease, it is necessary to know the specific type of cancer that affects them, not just the general category. The leukemias and lymphomas are less common and account for about five percent of all cancer cases. This group arises from cells of the blood, bone marrow, and immune system (including the lymph nodes). Melanoma (Skin Cancer) Melanomas, making up about four percent of all cancers, stem from the pigment- forming cells in the skin. This form of skin cancer may be aggressive. However, early diagnosis of melanoma with adequate surgical removal is often curative. Sarcomas are the least common group and account for only one percent of all malignancies. These tumors arise from the skeletal and connective tissues such as cartilage, bone, and muscle.