Starting at about age 20, you should examine your breasts every month, so that you can become familiar with their structure and detect any changes, such as lumps, that might indicate breast cancer. Most lumps are found by women themselves.
Do a self-examination about a week after your period ends; stand in front of a mirror and check the appearance of each breast for anything unusual - check the skin for puckering, dimpling, or scaliness; squeeze each nipple gently and check for discharge; raise one arm, and put it behind your head – use the sensitive pads of the middle three fingers of your other hand to check the breasts and surrounding areas thoroughly by feeling for any unusual mass under the skin (do this first standing up, then lying down); feel the entire breast and chest area under your armpit, up to the collarbone and all the way to your shoulder.
If you find any lumps, thickenings or changes, tell your doctor immediately.
Click here for more detailed breast self-examination tips.