Adenomyoepithelioma of the breast is extremely rare. It is was characterized by a bicellular pattern consisting of both epithelial cells and surrounding oval to spindel-shaped myoepithelial cells.
We report a case of the adenomyoepithelioma combined with fibroadenoma with prominent myoid differentiation.
The histologic immunohistochemical and ultrastructural findings revealed the two cell populations. The oval to spindle-shaped tumor cells were positive for S-100, protein and actin. In contrast, the cuboidal cells forming ducts were reactive for
cytokeratin, EMA and CEA. Cells with prominent myoid differentiation showed positive reaction for actin; however, They were negative for S-100 protein, desmin and cytokeratin. In ultrastructural examination, spindle cells showed tonofilaments in
the
perinuclear region, pinocytic vesicles along the plasmalemma and a continuous basal lamina. They also contained abundant myofibrils.
The authors postulate that the myoid components of the stroma have arisen in a milieu of myoepithelial cell hyperplasia.
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