IMMUNOHISTOCHEMICAL STUDIES OF MAMMARY TUMORS INDUCED BY THE DIRECT APPLICATION OF DMBA POWDER TO RAT MAMMARY GLANDS

Immunohistochemical studies were performed on locally growing finger tip-sized tumors induced by the direct dusting of 1 mg 7. 12-dimethylben_??_(a) anthracene (DMBA) powder to the right inguinal mammary tissue of both female and male 30-day-old Sprague-Dawley rats. A variety of benign and malignant tumors of epithelial and/or mesenchymal origin were detected histologically in both sexes of rats. In tumor tissues, as well as in normal mammary glands, immunoreactivity with actin distinctly demonstrated the myoepithelial cells. Type IV collagen clearly separated the parenchymal cells from the surrounding mesenchymal cell_??_. Normal periductal/intralobular mesenchymal cells of the mammary tissues were found only to be vimentin positive, whereas some neoplastic mesenchymal cells were found to express actin. Desmin was found in a few neoplastic mesenchymal cell_??_. This revealed that neoplastic mesenchymal element_??_ were composed of fibroblast, myofibroblast, and muscular nature.