Adenomyoepithelioma of the breast with malignant features

The clinico-pathological features of 7 cases of adenomyoepithelioma of the breast with features suggestive of malignancy are presented. There was a high incidence of local tumour recurrence, in 2 cases as high-grade infiltrating carcinoma of the breast of no special type ("ductal", grade III). One patient died as the result of a clinically diagnosed cerebral metastasis. Histological examination of the primary breast tumours reveals two main patterns: (1) tumours consisting in part of typical adenomyoepitheliomas but which merge with areas of obviously invasive malignant cells and (2) neoplasms that have the overall architecture of an adenomyoepithelioma but which, on close examination, are found to contain foci of cellular atypia and increased mitotic activity. The two patterns of tumour exhibit the same clinical behaviour and should be distinguished from adenomyoepitheliomas, which are cytologically bland throughout.