Unknown. There are some increased breast cancer risks associated with obesity, hormone medication use, early age at first menstruation, late age at first childbirth, etc. Only about 15% of breast cancers occur because of genetic inheritance. See this site with more information: http://media. Komen. Org/breastcancer101tool/english/video-player. Html#kbc_01_01.
Several. Family history, obesity, estrogen, being female, alcohol intake, decreased physical activity, and bad luck.
Listed. Good reference site: http://www. Cancer. Org/cancer/breastcancer/overviewguide/breast-cancer-overview-what-causes.