Ultrasound

An image of the breast that is made by exposing it to high-frequency sound waves.

When You Should Have It: To find out whether a suspicious lump is a solid mass or a fluid-filled cyst. Cysts are benign, except in rare cases, and can be drained with a needle. A solid mass may require a biopsy to determine if it is cancerous. Ultrasound may also be used to guide a needle biopsy.

What It Can Tell You: Besides showing whether a lump is a mass or a cyst, ultrasound is also being studied in women with dense breasts to see if it can help detect cancers that do not show up on mammograms.

Risks: False positives and false negatives.