Malignant Tumor--A mass of cancer cells. A malignant tumor may invade surrounding tissues or spread to distant areas of the body. (See "Metastasis" below)

Mammogram--The image produced by a low-dose X ray of the breast.

Mammography--A screening and diagnostic technique that uses low-dose X-rays to find tumors in the breast. Mammography can reveal a tumor too small to be felt even by the most experienced physician. The procedure may be used as a detection test in all women of the appropriate age group who do not have symptoms. All suspicious breast lumps must be biopsied to determine whether or not they are cancer.

Melanoma--A type of skin cancer. While most skin cancers rarely spread to other areas of the body and are easily treated and cured, melanoma can be more aggressive if not detected early.

Metastasis--The spread of cancer cells to distant areas of the body by way of the Iymph system or bloodstream. The term, metastases, refers to these new cancer sites.

Mitosis--The process of cell reproduction.

Monoclonal Antibodies--Antibodies designed to seek out chosen targets on cancer cells. They are under study to deliver chemotherapy and radiotherapy directly to a cancer, thus killing the cancer cell and sparing healthy tissue. Studies are also underway to determine if monoclonal antibodies can be produced to detect and diagnose cancer cells at a very early curable stage.

Morbidity--Sickness. The term usually refers to the proportion of people with an illness.

Mortality--Mortality rates reflect the number of deaths in a given population.