Expression of the c-myc oncoprotein in human metaplastic epithelial cells of fibrocystic disease.

Sections derived from fibrocystic disease in human breast tissue were examined for the presence of the c-myc oncoprotein by using the c-myc specific monoclonal antibody 9E10 (1). The results obtained revealed that the c-myc gene was not expressed in normal epithelial cells either of ducts or lobules. It was expressed mainly in mucous metaplastic cells and very rarely in apocrine cells. The c-myc protein was observed at a higher level in mucous metaplastic cells of epitheliosis and multiple papillomas. The number and intensity of positive mucous metaplastic cells was significantly increased after pretreating the sections with neuraminidase. We suggest that elevated expression of the c-myc nuclear oncoprotein in human breast metaplastic epithelial cells play a role in the early stages of malignant cell transformation.