Breast cancer occurs in the epithelial cells which line the ducts or lobules of the breast tissue. Breast cancer is malignant (cancerous) proliferation of these epithelial cells. Breast cancer is one of the leading cancers in women and among epithelial cancers breast cancer is the most common cancer among women. Breast cancer can occur only rarely if ever among men and the ratio of female to male is 150:1.

In regards to occurrence breast cancer is very common, but due to improved treatment in case of breast cancer the mortality has come down to a great extent in most of the countries where the cancer treatment facilities are available. Unlike other cancers, breast cancer has very good survival rate if treated properly. As compare to number of breast cancer detection every year, the number of deaths due to breast cancer is much less due to improved survival with adequate treatment.