What is a mammogram

What it is

A mammogram is an X-ray of the breast. Each breast is briefly compressed between two plates while low-dose X-ray images are taken, usually from two angles. The compression is uncomfortable for a few seconds but necessary: it spreads the tissue so small abnormalities show up and keeps the radiation dose low.

It is currently the most effective widely available test for finding breast cancer early, before any lump can be felt.

Screening versus diagnostic

Screening mammograms are done routinely in people with no symptoms, to catch cancer early. Diagnostic mammograms investigate something specific - a lump, pain, nipple discharge, skin changes, or an abnormal screening result - and involve more images and often ultrasound.

Who should screen and how often varies between countries and guidelines, and depends on age and personal risk, especially family history. The right schedule is a conversation between each person and their clinician, not a single universal rule.

What the experience is like

The appointment takes about 20 to 30 minutes; the compression itself lasts only seconds per image. Scheduling in the week after a period, when breasts are often less tender, makes it more comfortable.

Deodorants, antiperspirants, and lotions can show up on the images, so people are usually asked not to wear them on the day. Results go to the referring clinician, typically within days to a couple of weeks depending on the system.

Benefits, limits, and callbacks

The benefit is earlier detection: cancers found before they can be felt are generally smaller and more treatable. The radiation dose is low, and for most people the expected benefit of detection far outweighs it.

The limits matter too. Mammograms miss some cancers, especially in dense breast tissue, and they find some things that would never have caused harm (overdiagnosis). A callback after screening - being asked to return for more images - is common and is usually resolved as normal tissue overlap, not cancer: most callbacks do not end in a cancer diagnosis.

A normal mammogram never rules out a new lump that appears later. Any new breast change deserves assessment regardless of the last screening result.