Adenosarcoma is a biphasic neoplasm composed of malignant stroma and benign epithelium,
whereas adenofibroma is a biphasic neoplasm composed of benign stroma and benign epithelium. Adenofibromas are exceedingly rare, and there is a concern whether they truly exist or whether most cases are well-differentiated adenosarcomas.
See the image below.
Intraglandular polypoid projections characterize adenofibroma/adenosarcoma at low power (hematoxylin and eosin stain, x200).