While this is a good rule of thumb, the only way to know for sure is through the wisdom of your doctor and specialized medical tests, such as an ultrasound, a mammogram, or a fine needle aspiration, in which your doctor uses a tiny needle to extract a bit of the lump for a biopsy, or laboratory examination.
Another rule of thumb has to do with pain. Breast cancer does not usually present pain, but benign conditions often do, although there are exceptions to this as well.
Not all benign breast lumps will require additional testing, by the way.
If you find what appears to be a fluid-filled cyst during your menstrual period, your doctor may want to check your breast again at the end of your period to see if the cyst has disappeared.
If the cyst goes away, you and your doctor will know your lump was indeed benign and related to the hormonal fluctuations associated with menstruation.
A Variety of Benign Breast Lumps and Conditions That Are Normal
Most benign breast lumps and conditions are directly related to your menstrual cycle — to fluctuations in your hormones and to the fluid buildup that comes with your monthly period.
Other benign breast lumps and conditions may be related to plugged milk ducts, infections, and even breast injuries.
Here are some of the most common benign breast conditions: