Mammary Duct Ectasia Presenting As MRI Non-mass Enhancement in a RAD51C Carrier With Pituitary Adenoma.

Mammary duct ectasia is a benign breast condition that can mimic malignancy on MRI. We describe a woman with a pathogenic RAD51C variant who entered high-risk MRI surveillance at age 53 and was found to have segmental non-mass enhancement in the central left breast. MRI-guided core biopsy demonstrated duct ectasia with inspissated eosinophilic secretions, dense periductal lymphoplasmacytic inflammation with concentric fibrosis, and coarse microcalcifications without epithelial atypia or carcinoma. Her history included hyperprolactinemia from a growth hormone- and prolactin-positive pituitary adenoma diagnosed at age 41 and treated surgically, raising the possibility of an endocrine contribution to ductal dilatation and secretory stasis. This case emphasizes the importance of radiologic-pathologic correlation to avoid overdiagnosis while highlighting a potential link between long-standing hyperprolactinemia and mammary duct ectasia in susceptible patients.