There is described fifty-year-old woman with so called malignant adenomyoepithelioma of the breast. The conventional benign looking adenomyoepithelioma with biphasic tubular pattern continually fused to unequivocal invasive lesion which by immunophenotype turned out to be myoepithelial carcinoma. The 15 months follow up was uneventful. Extensive literature overview and terminology consideration is presented. The paper discusses biologic consequences of this rare breast lesion and its close resemblance to almost identical lesions in the salivary glands and skin adnexa.

        Key words: breast - adenomyoepithelioma - adenomyoepithelial adenosis - myoepithelial carcino- ma - epimyoepithelial carcinoma