Aspiration biopsy cytology of mammary myoepithelioma.

A case of ultrastructurally confirmed myoepithelioma of the breast studied by fine-needle aspiration biopsy is reported. Aspirated tumor cells were spindle-shaped with well-defined cytoplasm and oval nuclei showing no remarkable nuclear pleomorphism. They were seen mainly in irregular bundles with strong cellular cohesiveness. Their cytoplasm contained S-100 protein demonstrated by the peroxidase antiperoxidase staining technique.