Mammograms and breast ultrasounds are both vital imaging tools, but they serve different, complementary purposes.

A mammogram is a low-dose X-ray of the compressed breast. It is the gold standard for routine screening and early detection, particularly for identifying microcalcifications—tiny calcium deposits that can be early warning signs of cancer long before a lump is formed or can be felt. However, mammograms can be less accurate in women with dense breast tissue. A breast ultrasound uses sound waves to create real-time images without radiation. It is primarily a problem-solving tool used to distinguish between fluid-filled cysts and solid lumps, and to evaluate unclear areas on a mammogram.

Typically, a mammogram is the first-line screening test. If further clarification is needed, an ultrasound is added to provide a comprehensive assessment.

Frequently Asked Questions

Do I need a mammogram if I already had an ultrasound?

Yes. Mammogram and ultrasound are two different ways to image the breast. A mammogram uses X-rays and is good at detecting early breast cancer before a lump forms — these can appear as microcalcifications (small white spots). Ultrasound is good at evaluating lumps and masses, but it should NOT be considered a replacement for mammography, because many breast cancers can only be seen on a mammogram. Ultrasound is best used as an addition to screening mammography, particularly in women with dense breast tissue.

Are mammograms painful?

A mammogram uses low-dose X-rays to create images of breast tissue and can detect lumps too small to feel. During the scan, each breast is compressed for only about 20 to 30 seconds per view (usually two views per breast). The compression can be uncomfortable, but it is brief. Compression matters because it spreads and flattens the tissue for a clearer image and actually reduces the radiation needed. Since breasts are more sensitive in the two weeks before a period, it is best to schedule your mammogram for the week after your period, when they are usually less tender.

Do mammograms cause cancer because of radiation?

No. While mammograms do use a small amount of radiation, the risk of it causing cancer is virtually non-existent. The radiation dose from a standard screening mammogram is about 0.4 mSv — roughly equivalent to seven weeks of natural background radiation, or about the same exposure as a flight from Singapore to Tokyo. The benefit of detecting cancer early far outweighs this very small dose.

My last mammogram was normal — does that mean a new lump isn't cancer?

Not necessarily. Screening mammograms are important for detecting early cancer, but up to 20% of breast cancers can be missed on a mammogram. This is why it is important to stay breast-aware and perform regular self-examination between screenings. If you feel a new lump — even if your last mammogram was normal — see a doctor to have it assessed.