More than 4 million births are expected in the U.S. this year and at current estimated rates, breast cancer will be diagnosed in at least 1300 of these pregnancies. While this constitutes only a small percentage of the total number of cases diagnosed annually, this percentage will probably rise due to the trend toward delay of childbearing. Although pregnancy at an early age, and repeated pregnancies, actually appears to decrease the lifetime risk of developing breast cancer, even among higher risk groups, finding the disease during a pregnancy seems to be associated with a poorer prognosis. However, the poorer outcomes do not appear to be due to the pregnancy itself, or to the type of breast cancer that develops, but due to the fact that when breast cancer is found during pregnancy, it has a greater likelihood of being at a more advanced stage. Indeed, about 50% of breast cancer cases found during pregnancy already have metastatic disease at the time of diagnosis
Since routine mammography is not recommended during pregnancy, breast cancer is usually suspected by detection of a painless 'lump’ in the breast. Unfortunately, the breasts normally become ‘lumpier’ throughout pregnancy as the soft tissues and milk ducts enlarge in preparation for lactation. Even when a more prominent ‘lump’ is detected, it is often ignored at first (and more than 80% are likely to be ‘benign’), thereby, instilling some delay in early diagnosis. The index of suspicion rises if there is bloody discharge from the nipple, pain in the breast, skin changes over the lump or nipple, or prominent lymph nodes found in the axilla. A thorough breast and lymph node exam by your provider at your earliest obstetrical visit, ongoing self-assessment, and a low threshold of changes you consider to be significant, can help improve the prospects for an earlier diagnosis during pregnancy.
Once a suspicious ‘lump’ is detected, it is very important that efforts at diagnosis are undertaken, immediately, and not delayed until after delivery, regardless of the gestational age at which the ‘lump’ is found. A variety of noninvasive imaging studies are available to assess the location and appearance of a breast mass, but in the end, if cancer is suspected, or ‘cannot be ruled out,’ some kind of invasive diagnostic study is necessary to provide a ‘tissue diagnosis.’
The same noninvasive diagnostic studies that are available for women who are not pregnant, are often used with some special precautions taken with regard to the fetus during pregnancy. The first technique that is usually offered is ultrasound. Ultrasound of the breast is considered completely ‘safe’ for the fetus and can be used to distinguish between a simple fluid-filled cyst and a solid mass. Although many imaging specialists do not rely on ultrasound to assess whether a solid mass appears benign or malignant during pregnancy, one recent study suggested that it was highly effective when used to follow-up known cancers and lymph node metastases in pregnant women undergoing chemotherapy (Yang WT, et al., Radiology 2006;239:52-60).
Mammography is an x-ray study that could potentially expose the baby to small amounts of radiation. The total radiation dose required for the average mammogram falls well below usual limits of concern for a baby, but the added precaution of a lead shield placed on the maternal abdomen is usually taken, especially in early pregnancy. Routine mammography during pregnancy is not recommended, but even when a ‘lump’ is felt, mammography helps to correctly identify no more than about three-fourths of cancers under optimal conditions.
Magnetic resonance imaging (MRI) is also probably safe for the fetus during pregnancy, especially when directed at the breast, because it does not use any form of ‘ionizing radiation,’ although there is limited experience with this modality in pregnant women for this purpose. It is also extraordinarily expensive when compared to ultrasound and mammography. If your provider feels that this will help to rule out the possibility of malignancy, then it can be considered, but if either ultrasound or mammography has raised concerns of malignancy, the next best step is to proceed with a ‘tissue diagnosis.’
A tissue diagnosis can usually be accomplished by a simple fine-needle aspiration or core biopsy. These can be done with direct ultrasound guidance to improve the prospects that the sample is taken from the ‘lump’ of concern or the greatest area of abnormality detected by the imaging studies. Occasionally, it is necessary to perform an open, excisional biopsy, but if this is necessary, it can often be done under local anesthesia, posing minimal risk to the fetus.
If a cancer diagnosis is established, your doctor will probably want to perform other studies to establish the actual ‘stage’ of disease. This may be necessary so that proper advice regarding treatment options during and after the pregnancy can be discussed. As part of this evaluation, a chest x-ray is often done to look for evidence of metastatic disease in the chest. Again, the total dose of radiation to the baby is low and can be further reduced by abdominal shielding. Ultrasound can be used to look for metastatic disease in the liver and, if necessary, an MRI can be done to look for brain metastases. A ‘bone scan’ can be done to look for metastatic disease and also requires very low doses of radiation.
Even in the absence of overt metastatic disease, it is usually important to know if the cancer has spread to the local lymph nodes draining the breast. For years, breast cancer specialists have looked for ‘sentinel lymph node’ involvement as a means of staging the disease, minimizing surgical intervention, and providing recommendations for therapy. Another recent study has shown that using a radioactive compound (99mTc-sulfur colloid) can successfully accomplish identification of the sentinel lymph node even during pregnancy with minimal risk of radiation exposure to the baby (Pandit-Taskar N, et. al., J Nucl Med 2006;47:1202-8).