Breast cancer is the most common cancer among women worldwide, excluding nonmelanoma skin cancers. Approximately one in every ten women in the United States will develop the disease at some point during her lifetime.

Contrary to popular belief, however, breast cancer is not solely found among women. The disease also occurs in men, though with much less frequency. Fewer than one in every 1,000 men develop malignancies of the breast.

Increased awareness of breast cancer has resulted in increased funding for many research programs dedicated to discovering potential causes of and cures for the disease. Consequently, breast cancer has been much better characterized than many other types of cancer. Researchers have linked the disease to specific genetic mutations in the genes designated HER2, BRCA1, BRCA2, and p53. Knowledge of these mutations, which can be both inherited and acquired, may eventually lead to new ways to prevent and treat the disease.

The vast majority of breast cancers originate in the glandular tissues of the breast and are classified as adenocarcinomas. Both the lobular tissues, which produce milk, and ductal tissues, which are involved in the transfer of the milk to the nipple, are considered glandular tissues and, therefore, may give rise to adenocarcinomas. The most common variety of adenocarcinoma is known as infiltrating ductal carcinoma, a tumor that usually manifests itself as a single hard lump not easily movable. Nearly 80 percent of all cases of breast cancer diagnosed are infiltrating ductal carcinomas.

Risk of developing breast cancer rises as women get older. Most malignancies develop around the time of menopause, about 75 percent of cases involving women 50 years of age or older. The disease can strike at any time, however, and it is widely recommended that all women over the age of 20 perform a monthly self-examination of the breasts. Most medical societies also suggest that women 40 and older receive mammograms on an annual basis. Such emphasis on detection is reflective of the fact that while breast cancer cannot be readily prevented, early discovery of the disease can greatly reduce the risk of developing advanced cancer, which is generally much more difficult to treat.

Breast Adenocarcinoma at 20x Magnification - The most common treatment for breast cancer is surgery with adjuvant chemotherapy or radiotherapy. Surgical procedures for the disease range from conservative lumpectomies, in which only the tumor is removed, to radical mastectomies, which involve the complete removal of the breast, underlying muscle, and other tissue.

Breast Adenocarcinoma at 10x Magnification - The month of October is designated by many charities and health organizations as a time to increase awareness of breast cancer and is commonly associated with the pink ribbons many individuals wear in order to symbolically recognize the struggles of men and women faced with the disease.

Breast Adenocarcinoma at 20x Magnification - Breast cancer treatment sometimes entails chemotherapy or radiotherapy without accompanying surgery, or biological therapy, which involves the utilization of inhibitory drugs to block hormones that normally promote growth of cancer cells.