If a clinical breast exam identifies a lump, calcifications that look suspicious are seen on a mammogram, or an ultrasound or MRI identifies an area that looks abnormal, a biopsy allows the doctor to determine if the lump or suspicious area is benign (not cancer) or cancer.

A biopsy provides important information. With some types of tumors, such as tumors of the ovary or pancreas, it is possible for a needle to carry a malignant cell to another area. But this is not a concern in breast cancer. Breast cancer cells do not seem to be able to live independently unless they are biochemically ready to do so. This means that the biopsy procedure will not spread the cancer to other areas.

In the future, surgeons will probably have ways to identify whether cancer is present without doing a biopsy. Right now, though, the only way to determine if cancer is present is by doing a biopsy of the lump or microcalcifications, or completely removing the lump, and examining the cells under a microscope.