Breast disease in the pregnant and lactating patient: radiological-pathological correlation
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Substantial physiological changes occur during pregnancy and lactation, making breast evaluation challenging in these patients. This article reviews the imaging challenges of the breast during pregnancy and lactation. The normal imaging appearance, imaging protocols and the imaging features of each commonly encountered benign and malignant entity with pathological correlation and supporting examples is described. An awareness of the imaging features of the breast during these physiological states and of various benign and malignant diseases that occur permits optimal management.
Evaluation of the pregnant and lactating patients who present with a breast problem is challenging. Although ultrasound may characterise the finding in many cases, mammography and even MRI may have a role in the management of these patients.
• To review physiological changes of the breast during pregnancy and lactation
• To review imaging protocols of the breast during pregnancy and lactation
• Discuss imaging findings with pathological correlation of benign and malignant diseases in pregnancy and lactation
• Discuss pathological correlation of imaging findings in pregnancy and lactation
KeywordsBreast Disease Lactating Pregnancy Ultrasound MRI
Pregnancy-associated breast cancer occurs with a frequency of one in 3,000–10,000 pregnancies, accounting for 1–3 % all breast cancers . It is not infrequent for women to present to their physicians with a breast problem during pregnancy or within 1 year of delivery. Changes occurring in the breast during these physiological states make clinical and radiological evaluation of these patients challenging. Improving understanding of varied breast problems and their imaging appearance on multiple modalities is essential to ensure optimal management of these patients.
In the first and second trimester, there is proliferation and differentiation of the lobules, alveoli and lactiferous ducts, the alveolar epithelium becomes secretory. With rising serum prolactin during the third trimester, the milk-producing cells continue to differentiate and colostrum eventually fills the alveoli and milk ducts prior to delivery. These proliferative changes result in bilateral breast enlargement and increased overall density of the breast tissue on imaging. Following delivery, the lactogenic effect of prolactin results in a substantial increase in milk production. All of these physiological changes directly impact the imaging appearance of the breast on mammography, ultrasound and magnetic resonance imaging (MRI) thereby complicating evaluation of pregnant and/or lactating patients, presenting with a breast problem.
Imaging protocols and challenges
Radiological evaluation varies depending upon the age of the woman, her pregnancy and lactational status. Subsequent to a clinical history and thorough physical examination, patients are frequently imaged to determine whether there is an underlying abnormality to account for the patient’s symptoms. For pregnant and lactating women under the age of 30 years, ultrasound is the initial imaging test of choice given the lack of radiation exposure. Mammogram could be considered in these patients if ultrasound is negative or it reveals indeterminate, suspicious or no findings . Lactating women over 30 years of age are typically imaged using both mammography and ultrasound. In an effort to reduce the overall breast density, lactating patients are encouraged to express milk immediately prior to imaging. In a pregnant patient, mammography should be performed, if ultrasound reveals a suspicious finding or if biopsy of a solid lesion reveals malignancy. A complete evaluation of a pregnant patient with a lump should not be delayed until after delivery, because of fear of radiation. Without shielding the abdomen, the dose to the fetus from a four-view mammogram is 0.4 mrad, much less than background, and with shielding, the risk is not significant and safe to the fetus . Fetal malformations are known to occur at a dose exceeding 10 rads .
The National Comprehensive Cancer Network guidelines for clinical practice in pregnant patients with breast cancer or suspected to have breast cancer, states that “mammography of the breast with shielding can be safely done” [4, 5].
Normal imaging appearance of the breast in pregnancy and lactation
Ultrasound has a better sensitivity in pregnant and lactating patients, ranging from 86.7 to 100 % [8, 9]. On ultrasound, the breast predominantly appears diffusely hypoechoic during pregnancy due to enlargement of the non-fatty fibroglandular component (Fig. 1c), whereas during lactation there is diffuse hyperechogenicity with prominent ducts and vascularity during lactation  (Fig. 1d). Typical imaging findings for breast cancer on ultrasound are hypoechoic to isoechoic irregular mass with or without associated posterior shadowing; occasionally there may be posterior acoustic enhancement due to central necrotic components. Colour Doppler helps assess vascularity of the mass lesion.
If breast MR is performed, the ACR practice guidelines recommend that it is safe for the mother to continue breast-feeding after receiving gadolinium. If the mother remains concerned about any potential ill effects, she should be given the opportunity to make an informed decision as to whether to continue or temporarily abstain from breast-feeding after receiving a gadolinium contrast medium. If the mother so desires, she may abstain from breast-feeding for 24 h with active expression and discarding of breast milk from both breasts during that period. In anticipation of this, she may wish to use a breast pump to obtain milk before the contrast study to feed the infant during the 24-h period following the examination .
Breast diseases in the pregnant and lactating patient
A wide variety of benign and malignant breast problems may be encountered in these patients. Due to physiological changes, the most commonly encountered problems are lactational change/lobular hyperplasia, lactational adenoma and lactational calcifications.
Benign entities include galactocele, fibroadenoma, obstructed milk duct, mastitis with or without abscess, hyperplastic intramammary and/or axillary lymph nodes, and granulomatous mastitis. Malignant diseases include pregnancy-associated breast cancer and metastatic disease.
Lactational changes/lobular hyperplasia and/or lactational adenoma
Enlargement of axillary breast tissue
The embryonic mammary ridge (milk line) extends from the axilla to the groin. Incomplete regression of this ridge during embryological formation gives rise to ectopic breast tissue.
Accessory breast tissue occurs in up to 0.2–6 % of the general population . Ectopic breast tissue is subject to the same hormonal influences and risk of disease as eutopic breast tissue. During menses or pregnancy, hormonal stimulation can cause engorgement and discomfort. As a consequence, these patients typically complain of fullness and discomfort in this area. Ectopic breast tissue can undergo lactational change during pregnancy, and in the presence of a nipple-areolar complex it can give rise to lactation . The axilla is the most common site in which accessory breast tissue can be found . On mammography, ultrasound and MRI, accessory breast tissue has the imaging appearance of normal breast tissue. Primary carcinoma of ectopic breast tissue has been reported only in a small number of cases .
Obstructed milk duct
Acute bacterial mastitis will either resolve with antibiotic therapy or evolve into an abscess if treatment is delayed or inadequate. Approximately 4.8–11 % of lactation-related mastitis is complicated by breast abscesses . Infection is most commonly due to S. aureus (with increasing cases of methicillin-resistant S. aureus MRSA) and Streptococcus. The patient presents with fever, chills, tenderness and breast erythema. Imaging with ultrasound can confirm the diagnosis, provide a means to drain the collection to tailor antibiotic therapy and can be safely used for regular follow-up of abscess. Ultrasound is the modality of choice and typically reveals a complex hypoechoic cystic mass of varied shape, commonly multiloculated with indistinct margins, peripheral vascularity and posterior acoustic enhancement (Fig. 9b); however, there should be no vascularity within the fluid collection . Mammography is performed only if unclear of diagnosis and may show signs such as mass, distortion, asymmetric density and skin thickening, which are not specific to cancer. Presence of suspicious calcifications is more specific for cancer . Percutaneous drainage combined with antibiotic therapy provides effective treatment. In some cases multiples drainages are required [35, 36, 37]. Warm compresses and frequent breast feeding also help to shorten the duration of symptoms. The presence of mastitis and/or abscess poses no risk to the breast feeding infant. Cessation of breast-feeding is necessary only when treatment with an antibiotic contraindicated for the newborn is prescribed (e.g. tetracycline, ciprofloxacin or chloramphenicol) or if surgical drainage is performed . Due to overlap of radiological findings in infection and inflammatory breast cancer, if there is clinical suspicion, strong family history or atypical course breast biopsy or skin punch biopsy should be considered.
Enlarged intramammary and/or axillary lymph nodes
Pregnancy-Associated Breast Cancer (PABC)
With a reported incidence of 1.7–6.6 %, metastasis to the breast most commonly occurs from the contralateral breast cancer, lymphoma/leukaemia, melanoma and lung carcinoma. Though, any tumour can metastasise to the breast, non-mammary metastatic lesions are rare. Imaging entails targeted ultrasound and diagnostic mammography. Most metastases appear as well-circumscribed masses which lack calcifications, although psammomatous calcifications may be seen if the primary is of ovarian or thyroid origin. Metastatic lesions are more likely multiple and bilateral and are often found in the subcutaneous fat, whereas primary breast cancers develop in glandular tissue. Percutaneous core biopsy permits diagnosis when clinically needed to guide management.
Substantial physiological changes during pregnancy and lactation make it challenging to evaluate patients presenting with a breast problem. Most findings in pregnant and lactating patients are benign. Ultrasound is the first-line imaging modality for all pregnant women and for lactating women less than 30 years of age. Mammography is indicated in lactating women over 30 years of age and in pregnant women with suspicious findings on the initial ultrasound or with a biopsy diagnosis of breast cancer. An awareness of the imaging features of the various benign and malignant diseases during these physiological states, permits optimal management.
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