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How to cite this article: Perez F, Bragg A, Whitman G. Pregnancy associated breast cancer. J Clin Imaging Sci 2021;11:49.
Pregnancy associated breast cancer (PABC) is a subset of cancer that is too often diagnosed at a more advanced stage due to physiologic changes of the breast and lack of awareness among patients and physicians, resulting in higher mortality rates. While PABC is rare, it is postulated that as women delay childbearing, the rate of PABC may increase. Therefore, it is important to discuss appropriate workup, safety of mammography during pregnancy, and biopsy techniques.
Pregnancy associated breast cancer (PABC) is defined as cancer diagnosed during pregnancy, within 12 months postpartum, or anytime while the patient is lactating. PABC is a rare condition which is increasing in incidence likely due to a combination of delaying childbearing together with an overall increase in breast cancer incidence. Although it is infrequent, occurring in 0.3 in 1000 pregnancies, it is the most common malignancy in pregnancy and the most common cause of cancer-related death in pregnant and lactating women. The diagnosis of PABC is often delayed and remains a challenge due to the underlying anatomical and physiologic changes of the breast during pregnancy and lactation. Early recognition of PABC is imperative as there is an expected increase in incidence as more women delay childbearing. In addition, PABC is associated with a mortality rate that is 50% higher when compared to non-PABC.
DIFFERENTIAL DIAGNOSIS OF A BREAST MASS IN A PREGNANT OR A LACTATING WOMAN
The breast may be affected by a variety of physiologic changes and disorders during pregnancy and lactation, which range from benign masses, including cysts, to infectious or inflammatory processes. A breast mass during pregnancy and lactation most often does not represent malignancy. The most common benign masses during this time period include fibroadenomas, galactoceles, and lactating adenomas. Fibroadenomas are the most common breast masses in women between the ages of 25 and 40 years and fibroadenomas tend to regress in size after the age of 40 years. Due to hormonal influences during pregnancy and lactation, fibroadenomas may demonstrate an increase in size or even infarct. Galactoceles are breast masses commonly seen during lactation and present as complicated cystic masses with fat-fluid levels. Lactating adenomas are seen late in the third trimester and during lactation. The sonographic appearance of lactating adenomas is often indistinguishable from that of fibroadenomas.
APPROPRIATE IMAGING WORKUP OF PREGNANT AND LACTATING WOMEN
The workup of a mass in a pregnant or a lactating patient begins with an ultrasound [Figures 1 and 2]. The benefits of sonographic imaging include high sensitivity and a lack of ionizing radiation. Some studies have reported sensitivities and negative predictive values has high as 100%. An additional benefit of ultrasound is that it can detect and characterize benign breast masses.
Mammography is considered generally safe during pregnancy and lactation. The radiation dose from a bilateral two view mammogram is <3 mGy per view, which is roughly equivalent to 7 weeks of background radiation. The radiation dose to the uterus is <0.03 microGy, which is a fraction of the 50 microGy threshold that is known to cause teratogenic fetal effects. In addition, a lead apron shield can be used to decrease the dose to the uterus by up to 50%. Despite the relative safety of mammography during pregnancy and lactation, mammography is only indicated if there is a strong suspicion of malignancy or if malignancy has been proven by core needle biopsy [Figure 3].
The sensitivity of mammography, which normally ranges from 78% to 90%, decreases drastically during pregnancy and lactation. The discrepancy between the sensitivities of mammography and ultrasound [Figure 4] results from the increase in parenchymal density due to hormonal influences, resulting in a decrease in mammographic sensitivity. The benefits of mammography are that microcalcifications are detected more easily compared to ultrasound, when associated calcifications are present, mammography can be helpful in the determination of the extent of disease including multicentric and multifocal disease.
BIOPSY TECHNIQUES AND POTENTIAL RISK OF BIOPSY IN A PREGNANT OR LACTATING WOMAN
Ultrasound-guided biopsy is the preferred method of tissue sampling due to the lack of ionizing radiation and ease of the performance. However, stereotactic biopsy and mammography-guided wire localization are safe during pregnancy and can be performed. MRI-guided biopsy is not recommended in pregnancy due to the gadolinium-based contrast agent crossing the placenta and small quantities of gadolinium dissociating in the amniotic fluid and dissolving into toxic free gadolinium ions. However, MRI-guided biopsies are safe in lactating women. In addition to the usual risks of bleeding and infection, there is a small risk of milk fistula. This risk is mitigated by feeding or pumping immediately before the biopsy and resuming shortly after and also using a 14 g needle or smaller.
PABC is a rare condition that is increasing in incidence possibly due to women choosing to delay childbearing in conjunction with an overall increase in breast cancer. There are many factors to consider when imaging pregnant and lactating patients, such as radiation exposure to the breast and the fetus in addition to the risks of performing biopsies. Early detection of breast cancer can decrease morbidly and mortality in this group of patients.
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