Screening for Breast Cancer During Pregnancy

Your breasts undergo amazing changes when you become pregnant. As they develop milk ducts for breast feeding, they often double in size and become heavy with extra fluid. The breast tissue also feels more firm and "lumpy bumpy." These changes can make it difficult to diagnose breast cancer. Concern about how an imaging technique affects a developing baby also may limit some of the diagnostic options for women with a suspected breast cancer.

Several small studies have looked at how breast cancer is most often first detected during pregnancy, and the safety and reliability of mammography, ultrasound, and other breast cancer imaging techniques during pregnancy.

Signs of breast cancer during pregnancy

Most breast cancers during or shortly after pregnancy first appear as a painless breast lump. But between 70% and 80% of the breast lumps detected during pregnancy are NOT cancerous.

It's reassuring to know that if you develop a breast lump during pregnancy, it is unlikely to be breast cancer. But you should still bring any suspicious lump to the attention of your doctor and go through the proper tests to find out whether it might be cancer. DO NOT WAIT UNTIL YOU DELIVER OR STOP BREAST FEEDING TO GET THE LUMP CHECKED OUT.

So, if you're pregnant and you have a breast lump that needs checking, which tests are safe for you and your baby?

Mammograms

Mammography during pregnancy may be considered for women with signs or symptoms of a possible breast problem.

Small studies have found that mammography poses little to no harm to the fetus during pregnancy if a lead shield is placed on the belly to block any possible radiation scatter.

But the accuracy of mammography is limited during pregnancy. In three different studies, the percentage of breast cancers in pregnant women that mammography detected was between 62% and 78%. This is significantly lower than the average 85% detection rate in non-pregnant women.

Regular screening mammography in women without any symptoms is not done during pregnancy.

Ultrasound

Ultrasound is considered a safe tool for "seeing" inside the breasts of pregnant women. It is usually used before mammography to evaluate a palpable lump (a lump you can feel).

In both pregnant and non-pregnant women, ultrasound can accurately tell if a lump is a harmless cyst filled with fluid, or a solid mass that could be cancerous. But it is much less accurate at distinguishing between a solid lump that is breast cancer and a solid lump that is not.

MRI

In the past, doctors questioned whether Magnetic Resonance Imaging (MRI) was safe during pregnancy. Nowadays, MRI is sometimes used to check breast lumps in pregnant women that look on a mammogram like they might be cancerous. Talk to your doctor about whether this type of test is safe for you and your baby.

Biopsy

To diagnose breast cancer with certainty, in both pregnant and non-pregnant women, doctors need to remove a small portion of the suspicious breast lump. This procedure is called a biopsy. Such tissue can be removed by a needle (needle or core biopsy) or by surgical removal of the entire lump (excisional biopsy). Excisional biopsies tend to be more accurate than needle biopsies.

But interpreting the biopsy results can be difficult during pregnancy. A lot depends on the experience of the pathologist who looks under a microscope at the tissue that's removed. Because the breast cells of pregnant women are rapidly dividing, they can be confused with rapidly dividing cancer cells.

At least two studies have suggested that needle biopsies can accurately diagnose breast cancer in pregnant women. In the largest study of 331 pregnant or breastfeeding women, needle biopsies detected all the breast cancers present. Equally important, the needle biopsies did not falsely suggest the presence of a breast cancer in any women who were actually cancer-free.

Studies have also found that needle biopsies are safe in women who are breastfeeding. The risk of infection is higher with excisional biopsies because more surgery is involved, and breast milk can leak into the surgery area. If you are breastfeeding when you have an excisional biopsy, studies suggest you can reduce the risk of infection by stopping breastfeeding beforehand. You can further reduce milk production with ice packs and breast binding. You can also take a pill called bromocriptine to lower the level of the hormone that stimulates breast milk production. You take it several times a day, one week before the biopsy. To reduce the risk of infection even more, some doctors also prescribe antibiotics.