FLOW CYTOMETRIC ANALYSIS OF ESTROGEN-RECEPTORS IN RELATION TO HISTOPATHOLOGIC CHARACTERISTICS OF DMBA-INDUCED MAMMARY-TUMORS IN RATS

Experimental DMBA (7,12-dimethylbenzanthracene)-induced mammary tumours in Sprague-Dawley rats are studied. Percentages of the distinct types of adenocarcinomas (STEVENS et al. 1965) were as follows: type A (poorly-differentiated), 8.8%; type B (well-differentiated), 65.5%; type C (atrophic), 15.5% and type D (secretory), 5.4%. 51% of the mammary adenocarcinomas were seen to be positive to oestradiol receptors by means of flow cytometry; type A adenocarcinomas were found to be the most frequent positive tumours (88.9% positive cases) whereas the last adenocarcinomas to appear (type D) were negative. These results suggest that the oestradiol-sensitivity of DMBA-induced mammary adenocarcinomas decreases as the post tumour-induction period lengthens.