TY  - JOUR
T1  - Epithelial-myoepithelial Neoplasms of the Breast: Diagnostic Challenges and Emerging Molecular Features 
AU  - Wei, Shi
JF  - Journal of Clinical and Translational Pathology
VL  - 
IS  - 0
SN  - 2771-165X
SP  - 
EP  - 
Y1  - 2026-12-30
DO  - 10.14218/JCTP.2026.00045
UR  - https://www.xiahepublishing.com/2771-165X/JCTP-2026-00045
AB  - Background and objectives 
Epithelial-myoepithelial neoplasms of the breast are biphasic tumors composed of both epithelial and myoepithelial cell populations. Their rarity, broad morphologic spectrum, and evolving molecular characterization pose substantial diagnostic challenges, underscoring the need for an integrated review of their diagnostic and molecular features. This review aims to provide a comprehensive overview of epithelial-myoepithelial neoplasms of the breast, emphasizing their morphologic spectrum, diagnostic challenges, and emerging molecular features.
Methods
This narrative review is based on a review of the pertinent English-language literature and the author’s firsthand experience as a practicing breast pathologist.
Results
Benign epithelial-myoepithelial tumors include pleomorphic adenoma and classic adenomyoepithelioma. Pleomorphic adenoma of the breast closely resembles its salivary gland counterpart as well as the benign mixed tumor of the skin. In contrast, adenomyoepithelioma is unique to the breast and exhibits a broad spectrum of histomorphologic patterns. Most adenomyoepitheliomas follow a benign clinical course; however, atypical adenomyoepitheliomas may demonstrate more aggressive behavior, including local recurrence, malignant transformation, and, rarely, metastasis. Molecular studies have identified PLAG1/HMGA2 rearrangements in a subset of pleomorphic adenomas and recurrent HRAS Q61 and PI3K-AKT pathway alterations in adenomyoepitheliomas. In malignant adenomyoepithelioma, the malignant component may arise from the ductal epithelial cells, the myoepithelial cells, or both.
Conclusions
The rarity of epithelial-myoepithelial tumors, together with their marked histologic heterogeneity, makes them diagnostically challenging and underscores the potential for diagnostic pitfalls.