[A rare breast tumor of pluripotential cells]

A rare relapsing mammary tumor is described. The tumor consisted of a major mesenchymal component and a minor tubular one, there were many mitoses. Myofibrils, intercellular desmosomal contacts, basal membranes and secretory granules were found electron-microscopically. Coexpression of all intermediate filament (IF) proteins was found: total keratin, keratins of the liminal and myoepithelial types; IF specific for mesenchymal cells - vimentin, that for glial cells - glial acidic fibrillar protein and nerve cells - neurofilaments. Thus, as distinct from adenomyoepithelioma, the tumor is composed of pluripotential elements which are the exception from the rule of the IF proteins tissue specificity. The term "pluricelluloma" is suggested for this tumor.