Abstract: | Proliferating epithelial structures were studied immunomorphologically in 16 cases of fibrocystic disease and benign tumours. Monoclonal antibodies were used to prekeratin (PK) C12, normally specific for the lining epithelium, to prekeratin (PK) E3 and to the protein of intermediate filaments in mesenchymal cells--vimentin, normally specific for myoepithelium. The immunofluorescent analysis of the most common proliferating structures has shown that there are elements with a variable combination of PK C12, PK E3 and vimentin among the proliferating cells. While there are cells similar to normal lining epithelium (PK C12) or myoepithelium (PK E3) and/or vimentin), many cells have no analogues either among normal cells, or among cells from ductal, lobular and tubular tumour forms. Since in the most common forms of breast cancer only cells containing PK C12 were found, the immunofluorescent study with the application of monoclonal antibodies to PK C12, PK E3 and vimentin can be recommended in difficult and dubious cases for the recognition of carcinogenic or dysplastic nature of morphologically similar proliferating structures. |