The cause of most breast cancers is unknown. Genetic factors are involved in about 2% of cases, and women who are obese and/or eat a high fat diet, or drink a lot of alcohol are more at risk, but there is no clear cause in most cases. However, benign (harmless) lumps in the breast are very common, so you need to reassure women in your community that every change and every lump found in the breasts does not mean they have breast cancer. Only about one in every five women with a breast lump turns out to have cancer. The breasts are changing every month with the phases of the menstrual cycle, due to changes in the levels of the female reproductive hormones (oestrogen and progesterone), and sometimes these changes result in temporary lumps in the breast. Some women develop small painless lumps just before their menstrual period, which disappear after a few days. Sometimes a small tender cyst develops (a collection of fluid in the breast), which also disappears after a few days. If a lump is felt in the breast that remains for two weeks, it is wise to get it checked by a health professional.