Carcinoma of the breast (see also Chapter 17) is one of the most commonly diagnosed cancers in pregnancy. Although the effects of pregnancy on breast cancer progression are unclear, it has been consistently reported that breast cancers diagnosed during pregnancy are more likely to have higher grade disease with associated nodal involvement when compared with those diagnosed in nonpregnant women. This observation underscores the importance of expeditious evaluation of any breast mass in a pregnant woman. Physiologic breast changes in pregnancy include enlargement and glandular hyperplasia, both of which can limit the radiographic evaluation; however, imaging is essential to characterize any palpable mass. Ultrasound is typically the initial modality of choice in a pregnant woman, but mammography should be performed if needed. Biopsy is then required for any suspicious lesion, and if malignancy is discovered, surgery should not be withheld based on the stage of the pregnancy.
The treatment plan for patients found to have breast cancer in pregnancy needs to be individualized, and management should be multidisciplinary by a team with experience in treating high-risk pregnant woman and oncology patients. Chemotherapy frequently plays an important role in treating young women with breast cancer. Cytotoxic drugs are generally contraindicated in the first trimester, and termination of pregnancy is an option when the diagnosis of breast cancer is made at an early gestational age. Importantly, however, termination of pregnancy has not been demonstrated to improve maternal outcome, and the woman and her family should be counseled with this in mind. If the pregnancy is more advanced, chemotherapeutic agents may be administered during the pregnancy to avoid a delay in treatment. The decision to breastfeed should be made on a case-by-case basis and depends largely on what the treatment plan is during the postpartum period.