A mammogram is a low-dose X-ray of the breast that takes about 20 minutes from start to finish. The core of the procedure involves placing each breast between two plates, compressing it briefly, and capturing images. While the compression can be uncomfortable, each squeeze lasts only seconds, and the entire process is straightforward once you know what to expect.
How to Prepare Beforehand
Skip deodorant, perfume, lotion, and powder on the day of your appointment. Many deodorants contain aluminum, and those metallic particles show up on the X-ray as bright white specks that look nearly identical to calcifications, which are tiny calcium deposits that doctors specifically look for when screening for breast cancer. A radiologist at Memorial Sloan Kettering has described both as looking like “little grains of sand,” making them easy to confuse. Lotions create a different problem: they make your skin slippery, which can cause blurring during imaging because the technologist can’t hold the breast tissue firmly in position.
Wearing a separate top and bottom rather than a dress makes things easier, since you’ll only need to undress from the waist up. You’ll be given a front-opening gown or drape to wear during the exam.
If you still have periods, try to schedule your mammogram for the week or two after your period ends. Breasts tend to be more tender and swollen in the days leading up to and during menstruation, which can make the compression more painful than it needs to be.
The Step-by-Step Process
After you change into your gown, a technologist will guide you to the mammography machine, which looks like a tall, upright unit with two flat plates. You’ll stand facing it.
The technologist will ask you to open one side of your gown and help position your breast on the lower plate, called the breast support plate. The upper plate then lowers and presses down, flattening the breast firmly between the two surfaces. A screening mammogram captures two X-ray views of each breast, typically one from top to bottom and one from side to side. Each compression lasts just a few seconds while the machine takes its image.
You’ll then repeat the process on the other side. The whole imaging portion usually takes about 10 to 15 minutes. Once the technologist confirms the images are usable, you get dressed and leave. Most facilities send results within a couple of weeks, though some offer same-day results.
Why Compression Is Necessary
The squeezing is the part most people dread, but it serves two important purposes. First, flattening the breast spreads the tissue out so it doesn’t overlap in the image. Overlapping tissue can hide small abnormalities or create shadows that look like problems when none exist. Second, a thinner, compressed breast requires less radiation to produce a clear image, which lowers your overall exposure.
The pressure can range from mildly uncomfortable to genuinely painful depending on your breast sensitivity, the time in your cycle, and how much compression is needed. If it becomes too much, you can tell the technologist, and they’ll adjust. Some newer machines allow you to control the compression yourself, which research has shown can actually reduce breast thickness further (by nearly 2 centimeters in one study) because patients compress more steadily when they’re in control.
2D vs. 3D Mammograms
Traditional mammograms produce a flat, two-dimensional image that captures all the breast tissue in a single picture. This means small lesions can be hidden behind overlapping tissue. A 3D mammogram, called tomosynthesis, takes multiple images from different angles and reconstructs them into thin slices, similar to flipping through pages of a book. This layered view makes it easier to distinguish between dense tissue and actual abnormalities.
3D mammograms are increasingly common and detect cancers that 2D imaging can miss, particularly in women with dense breasts. The experience from the patient’s side is essentially the same: you still stand at the machine, your breast is still compressed, and the appointment takes roughly the same amount of time. The difference happens behind the scenes in how the images are captured and read.
Screening vs. Diagnostic Mammograms
A screening mammogram is the routine version, performed when you have no symptoms or known concerns. It captures two standard views of each breast. A diagnostic mammogram is ordered when something specific needs a closer look, whether that’s a lump you found, an area of concern from a previous screening, or symptoms like nipple discharge. The diagnostic version takes more X-ray views, focused on the area in question, and typically takes longer. A radiologist often reviews the images while you’re still at the facility so additional views can be taken immediately if needed.
What Happens With Breast Implants
If you have breast implants, you can and should still get mammograms, but the technique changes. Implants are opaque on X-rays and can obscure the breast tissue behind them. To work around this, the technologist uses a technique called implant displacement views: the implant is pushed back against the chest wall while the natural breast tissue is pulled forward and around it, allowing that tissue to be imaged clearly. This means more images are taken per breast, so the appointment runs a bit longer. Let the scheduling staff know about your implants when you book so they can allot extra time.
Understanding Your Results
Radiologists use a standardized scoring system called BI-RADS, which categorizes findings on a scale from 0 to 6. You don’t need to memorize the whole scale, but here’s what the most common results mean in practice:
- Category 0 means the images were incomplete or unclear, and you need additional imaging, like more mammogram views or an ultrasound, before a finding can be assessed.
- Category 1 means negative, with nothing abnormal detected.
- Category 2 means benign findings. Something was seen, like a cyst or calcification, but it’s clearly not cancerous.
- Category 3 means probably benign, with a follow-up mammogram recommended in six months to make sure nothing changes.
- Categories 4 and 5 indicate suspicious or highly suspicious findings that typically require a biopsy.
- Category 6 is used when cancer has already been confirmed by biopsy.
Getting called back for additional imaging is common and does not mean you have cancer. Many callbacks result in a category 1 or 2 finding once the extra views provide a clearer picture.
Breast Density and What It Means for You
As of 2024, mammography facilities are required by the FDA to include information about your breast density in your results letter. About half of women over 40 have dense breasts, which contain more fibrous and glandular tissue relative to fatty tissue. Dense tissue appears white on a mammogram, and so do tumors, which means cancers can be harder to spot. Dense breasts are also an independent risk factor for developing breast cancer.
If your results letter says you have dense breasts, it doesn’t mean anything is wrong. It means your screening picture is more complicated, and additional imaging like ultrasound or MRI may help catch things a mammogram alone could miss.
Current Screening Recommendations
The U.S. Preventive Services Task Force recommends mammograms every two years for all women aged 40 through 74 who are at average risk for breast cancer. These guidelines also apply to transgender men and nonbinary individuals assigned female at birth. If you have a family history of breast cancer, genetic risk factors, or other concerns, screening may start earlier or happen more frequently.