Breastfeeding and Breast Cancer

By Barbara Wilson-Clay, BS, IBCLC
The protective effect of breastfeeding in lowering the risk of breast cancer has been shown in a number of studies. The risk-reduction appears to be dose-dependent. That means, the longer the period of breastfeeding, the more the benefit. One study suggests that the greatest protection may occur when a little girl is breastfed and grows up to breastfeed her own children.
Unfortunately, lower risk does not mean no risk. Some women who have breastfed still get breast cancer. Women of all ages must check their breasts for changes and lumps and insist that their doctor takes their concerns seriously.

While it is rare, a very small percentage of women develop breast cancer during lactation. The pregnant or lactating breast can be lumpy. Doctors sometimes are distracted by the fact that a woman is breastfeeding and fail to take suspicious masses seriously. This can lead to delayed diagnoses.
In general, most lactation-related lumps are connected with episodes of plugged ducts and mastitis. They typically are tender, smooth, round, and movable. These breast symptoms should resolve within a few days with appropriate treatment. 

Warning signs for breast cancer are masses that feel “fixed” (they don’t move), puckering of the skin over the mass, and a mass that doesn’t go away after treatment for plugged ducts, mastitis, or abscess. Spontaneous clear or bloody nipple discharge should be reported.  Repeated episodes of mastitis in the same area of the breast may be of concern because an underlying problem (such as a tumor) could be causing it to reoccur. A rare form of breast cancer may appear as a red breast with no fever. Paget’s Disease of the nipple (a type of cancer) can be mistaken for a persistent fungal infection or as eczema of the nipple. It generally appears only on one nipple. All concerns should be discussed with your health care professional.

Mammograms can be performed on pregnant or lactating breasts. A mammogram during lactation will be easier to interpret if the breast is well emptied just before the test. Ultrasound is well-suited for examining breast lumps in pregnant or nursing mothers. Sometimes ultrasound is used to guide a hollow needle that aspirates material out of a lump so that the cells can be examined. This is called a needle biopsy. The most definitive way to rule out cancer is with a biopsy that removes the mass. While it may be very necessary, biopsy is also the most invasive procedure. To reduce scar tissue that may complicate lactation, the surgeon can make a radial incision, (like the spoke of a bicycle wheel), which may be less damaging to the breast than one following the curve around the areola.

If breast cancer is diagnosed, mothers typically face emergency weaning, surgery, chemotherapy and/or radiation treatments. Today, many patients choose breast-conserving surgery. While radiation therapy typically kills the milk-making tissue in the breast along with the cancer, there have been several cases of partial milk production in women who later gave birth.

Many women now get pregnant and breastfeed after being treated for breast cancer. If a woman has difficulty making a full milk supply, a Supplemental Nursing System™ can be used to help supplement baby at breast. Breastfeeding on one breast following mastectomy can be a very life-affirming experience. Breastfeeding is not considered to increase the risk of recurrence of cancer.

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Kim Y, et al. Dose-dependent protective effect of breastfeeding against breast cancer among ever-lactated women in Korea. Eur J Cancer Prev 2007; 16(2):124-9.
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