Radiologic and Pathologic Correlation for Lactating Adenomas

Lactating adenomas are benign breast lesions that occur in pregnant, lactating, and postpartum women. These lesions have no associated malignant potential; their origin is disputed with no consensus on whether they represent hyperplastic or neoplastic processes. On ultrasound, lactating adenomas are classically described as solid, circumscribed, parallel masses with iso/hypoechoic internal echotexture and posterior enhancement. Histologically, lactating adenomas appear as circumscribed nodules of tightly packed lobular acini with extensive lactational change during pregnancy or the postpartum period. Masses in pregnant and lactating women with probably benign imaging characteristics—oval, circumscribed, parallel, iso/hypoechoic—can be managed with short interval follow-up (BI-RADS 3) rather than biopsy. However, lactating adenomas can also demonstrate characteristics that overlap with pregnancy-associated breast cancer, such as margins that are not circumscribed, prompting biopsy to exclude pregnancy-associated carcinoma. Breast imaging radiologists must be aware of the variable appearances of lactating adenomas to appropriately manage pregnant and lactating women presenting with palpable lumps.