The Clinical Presentation, Management, and Outcomes of Breast Adenomyoepithelioma: A Single-Institution Experience.

Background: Adenomyoepithelioma (AME) of the breast is a rare biphasic neoplasm characterized by proliferation of epithelial and myoepithelial cells. Although most AMEs demonstrate indolent behavior, malignant transformation has been reported, and diagnostic uncertainty often complicates clinical management. Given the rarity of AME, most data are limited to case reports and small series, leaving optimal management undefined. Objectives: To describe the clinical presentation, imaging characteristics, histopathologic features, and outcomes of patients with breast AME. Design: Retrospective single-institution case series. Methods: We retrospectively reviewed 15 patients diagnosed with breast AME between 2010 and 2023. Demographic, clinical, imaging, core needle biopsy (CNB) findings, surgical pathology, and outcomes data were analyzed. Results: The median age at diagnosis was 56 years. More than half of the patients (53.3%) were asymptomatic at presentation. Mammography most frequently demonstrated discrete ovoid masses (61.5%), and ultrasound most often showed hypoechoic lesions (66.7%) with lobulated margins (50%). Core needle biopsy identified benign AME in 38.4% of cases, while 61.5% yielded indeterminate findings with AME included in the differential. Five patients underwent CNB alone without surgical excision. Of the 9 patients who underwent both CNB and excision, 6 (66.7%) had AME on final pathology, whereas 3 were upgraded (2 invasive carcinoma, 1 atypical ductal hyperplasia). Of the 3 cases with cytologic atypia on CNB, 1 was upgraded to invasive carcinoma. Over a median follow-up of 10 months, no recurrences, metastases, or breast cancer-related deaths were observed. Conclusions: Breast AME generally follows a benign clinical course, but diagnostic challenges exist due to histologic heterogeneity. Core needle biopsy features such as cytologic atypia may indicate higher malignancy risk. These findings highlight the ongoing dilemma of when observation is sufficient versus when surgical excision is warranted. Our results add to the limited body of evidence and align with prior reports, underscoring the need for larger, multicenter studies with longer follow-up to clarify long-term outcomes and optimal management strategies.