Introductionbreast cancer, cancer that originates in the breast. Breast cancer is the second leading cause of cancer death in women (following lung cancer). Even allowing for improvements in detection (i.e., the introduction of routine mammography), there has been a long-term gradual increase in the incidence of breast cancer since the early 1970s, but because of the more effective treatment afforded by such early detection, overall mortality began to decrease by the mid-1990s. Breast cancers can arise in the lobes or lobules (lobular carcinoma) or in the ducts (ductal carcinoma) of the breast. Lobular carcinoma often affects both breasts.
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