Abstract
Since there are controversial reports in the literature on 16 alpha-hydroxylase activity in human breast tumors, we have studied this enzyme activity in "normal", benign and malignant breast tissues by measuring the conversion of estradiol to estriol. Whereas 8 out of 14 (58%) malignant tumors showed positive activity, none of the other tissues had any detectable 16 alpha-hydroxylase activity. These preliminary results, when combined with reports in the literature on animal and human tissues, appear to indicate that more extensive studies on this enzyme could be useful as it could be an additional metabolic marker in human breast cancer.