Pure malignant myoepitheliomas of the breast: an immunohistochemical study.

Myoepithelioma of breast are extremely rare. We report two cases of pure malignant myoepithelioma of the breast, utilising light microscopic and immunohistochemical methods for diagnosis. Both the cases presented as breast lump. Hematoxylin and Eosin (H&E) stained microscopic sections revealed a predominantly spindle cell tumor. Immunohistochemical work up was done. Case number one expressed positivity for vimentin, Smooth Muscle Actin (SMA), S-100 and CD10. Case number two expressed positivity for Vimentin, CD10 and p63. This led to the diagnoses of malignant myoepithelioma in both of them. Documentation of such cases prospectively and from archival material, using immunohistochemistry, is of extreme importance to assess the prevalence, various phenotypic patterns, long-term biological behaviour and to establish management protocols for malignant myoepithelioma.