Breast cancer diagnosis has increased steadily in the United States since the mid-1980s, but the death rate from breast cancer has also fallen steadily during the same period. Breast cancer occurs in men as well as women, but is much less common. Both the behavior of the disease and its treatment are similar to that in women. The exact way that breast cancer develops is not well understood. This is currently a major area of research.
Several factors affect a woman's chance of developing breast cancer.
Between 5 and10 percent of invasive breast cancer is related to the presence of a gene that confers a very high risk of developing the disease. Both BRCA1 and BRCA2 also carry an increased risk of ovarian cancer and some other malignancies. Only by doing a breast biopsy can a reliable diagnosis of breast cancer be made. The diagnosis can be inferred from the presence of a lump in the breast or from a suspicious finding on a mammogram, but a confirmed diagnosis can be made only by a biopsy. Benign breast disease may also produce breast lumps.