Breast Cancer Diagnostic Screening

Patient Expert

You probably know what a mammogram is - in fact, you've probably had one. But how about an MRI? And why do some women need a PET scan or CT scan - and some don't? The daunting array of cancer screening tests is less scary when you understand what each one entails, and what it might tell you.

If you're over 40, you've probably had at least one mammogram. The mammogram has been the breast cancer screening tool of choice for decades, and still is. Though far from perfect, it's a relatively simple, quick, and inexpensive way to determine if a woman's breasts are normal, or if they show evidence of disease.

Until recently, age 40 was the beginning of yearly mammograms for most women; two years ago, a U.S. Preventive Services Task Force report was released advising women to delay regular mammograms until age 50. The report said the number of women in their 40s benefiting by early detection of cancer via mammogram wasn't enough to offset the number who suffered emotional stress and physical pain due to negative biopsies performed as a result of "suspicious" mammogram results.

As a result of enormous controversy surrounding these new guidelines, the USPSTF backed off its position somewhat, saying that women should consult with their doctors about the appropriate age to begin screening for breast cancer, based on personal risk factors.

Whether you have your first mammogram at age 40, age 50, or as a result of feeling a lump, you'll know its results quickly - usually within a few days, or in some cases, within an hour or so. A radiologist will read the test (either on film, or digitally), and will let you know everything's fine - or it's not.

What happens when the radiologist sees something suspicious on that mammogram?

You continue down the diagnosis path.

An ultrasound is another simple, non-invasive test. Where a mammogram will detect a suspicious area - either something that's changed from the year before, or something that doesn't look like it belongs in the picture - an ultrasound can refine that view just enough to tell whether the area in question is solid, or liquid.

And what good does that do? If the suspicious area is solid, it requires more testing; if liquid, it's assumed it's a non-cancerous cyst, and your testing is over.

If the ultrasound rules out a cyst, then your doctor may request a biopsy, which will determine with almost complete accuracy whether the area is a cancerous tumor. Sometimes, however, it might be useful to get a clearer look at the area in question, before resorting to a biopsy. And MRI (magnetic resonance imaging) can provide that better look.

What does an MRI do? It uses a magnetic field, radio-frequency pulses, and a computer to produce a detailed image of your breast, from the inside out. Since the many images received show very thin "slices" of your breast, they can be put together and viewed from many different angles - unlike the images from an ultrasound or mammogram. An MRI gives a much more detailed image of the rather vague opaque area seen on a mammogram or ultrasound.

An MRI is like reading glasses; suddenly everything that was fuzzy looks clear. And oftentimes your doctor can spare you a biopsy, if an MRI clearly shows the area in question is simply a normal part of your breast, scar tissue, or something else other than cancer.

MRIs are also commonly used in women who've been diagnosed with breast cancer - to get a better view of the tumor and its location; and to search for other possible cancers.

Sometimes diagnostic screening is needed as a result of nipple discharge, particularly when the discharge is bloody. In this case, a test called a ductogram (or galactogram) is used to identify any abnormal mass in the milk duct right beneath the nipple.

The test is relatively quick and painless; a small amount of contrast dye is injected into the duct via the nipple opening, and an X-ray is taken. If a mass is detected, a biopsy usually follows.

PET/CT scans
If you're diagnosed with breast cancer, and it's determined there's a chance it's spread to other parts of your body, your doctor may order a precautionary PET scan or CT ("cat") scan, to determine if the cancer in your breast has spread to other organs: lungs, brain, or liver. A regular X-ray ("bone scan") can show if the cancer's spread to your bones.

Many women, upon hearing they have cancer, are anxious to have a full-body scan, feeling it'll tell them for sure whether or not cancer is present anywhere else. But these scans aren't necessary unless your oncologist orders them; there are other reasonably accurate ways to determine the possibility of metastasis (namely, examining the lymph nodes under your arm). So don't panic if your doctor doesn't believe you need any scans; s/he's the best one to make this determination.

If you do need a PET (positron emission tomography) scan or CT (computed tomography) scan, here's the process. You'll drink a contrast dye, or it'll be injected via IV. You'll wait about 60 minutes, then lie on an examination table. The scanner rotates around you and over you, while you lie very still. A number of different views will be taken by the technician, who's in a separate room, but still available to you via microphone.

Some people report this is a claustrophobic experience; if you feel you might be uncomfortable, talk with your doctor ahead of time; s/he may order a light sedative.

The scan itself takes about 2 minutes (for a CT scan), or 20 to 30 minutes for a PET scan. Thus the entire test, including waiting for the dye to take effect, can take up to about 90 minutes.

The technician administering the test will forward the results to a radiologist, who'll read them and report back to your doctor. You'll probably have to wait several days for test results.

Thankfully, most women diagnosed with breast cancer don't need these scans. They should only be ordered if there's reason to believe the cancer might have spread (metastasized) out of the breast and beyond the lymph nodes, to other parts of your body. And this so-called distant metastasis is the exception with breast cancer, not the rule.

Finally, what about follow-up scans? As a survivor, should you be having screening scans every year, along with your mammogram?

Again, you may think you'd feel better if there was a test that could tell you if the cancer had returned, before you could feel any symptoms. But there are good reasons why you won't have screening scans as part of your continuing care; for more on this, please read Follow-Up Care: Balancing Vigilance and Faith.