Breast Cancer

Introduction

Breast cancer is cancer of the breast where cancerous growth arises in the tissues of the breast. If the malignant growth arises in the lining of the ducts that carry milk from the milk-producing lobules to the nipple, the breast cancer is called ductal carcinoma. If the malignant growth arises in the lining of lobules, the breast cancer is called lobular carcinoma. Ductal and lobular carcinomas may grow only inside the ducts and lobules of the breast or may spread into adjacent tissue. If the cancer cells grow only inside the ducts or lobules, the disease is called ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS). Patients with DCIS or LCIS have a higher risk of invasive breast cancer. While ductal carcinoma and lobular carcinoma represent the most common breast cancers (about 85 percent of all cases for the former and 8 percent for the latter), there are other rare types of breast cancers, such as other epithelial carcinomas, sarcomas, lymphomas and Paget's disease of the nipple.

Epidemiology

Breast cancer is the leading cause of cancer death among women worldwide. More than 1 million women will be diagnosed with breast cancer in 2007 worldwide. Risk varies by over fivefold among societies, and the highest risk is in the industrialized nations. The American Cancer Society estimates that nearly one in eight women in the United States will have breast cancer in her lifetime. The 2007 statistics show that over 180,510 persons (178,480 for female and 2,030 for males) will be diagnosed with breast cancer (not including carcinoma in situ) and 40,000 people will die from the disease in the United States (Piccart, 102).

While breast cancer is the most common type of cancer among women, breast cancer also occurs in men. Male breast cancer is about 100 times less frequent than the disease in women. The incidence rate of breast cancer is low before 40 years of age, but the rate increases continuously and rapidly with age, and peaks at the oldest ages. In the United States, breast cancer is diagnosed more often in white women than in Latina, Asian, or African-American women. Incidence rates of breast cancer were reported to be increasing in the 1980s and 1990s; recent studies suggest that the increase has leveled off, and the reported earlier increase appears to be largely due to early detection through mammography screening. Breast cancer mortality is also declining, which can be largely attributed to early detection and better treatment (Jemal, 22).

Etiology

While considerable efforts have been made, little is known about the etiology of breast cancer. Breast cancer risk has been traditionally linked to menstrual and reproductive factors, and genetics. These factors can account for only about 25 percent of breast cancer cases. Thus, much of the etiology is still unexplained.

It is suggested that breast cancer is originated in utero. Exposure to higher levels of endogenous hormones in utero has been suggested to be a risk factor for female breast cancer. Neonatal jaundice has been linked to an increased ...