Breast cancer

 breast cancer , disease characterized by the growth of malignant cells in the  mammary glands. Breast  cancer can strike  males and  females, although women are about 100 times more likely to develop the disease than men. Most cancers in female breasts form shortly before, during, or after menopause, with three-quarters of all cases being diagnosed after age 50. Generally, the older a woman is, the greater is her likelihood of developing breast cancer. Worldwide, breast cancer is the most common cancer among women, and in North America and Western Europe, where  life spans are longer, the incidence is highest. In addition, in high-income countries, breast cancer is the leading cause of cancer death among women age 20 to 59.