Abstract
The precise place of local estrogen production in mammary cancer is still controversial. In this investigation localization of aromatase (the key enzyme of estrogen biosynthesis) was studied in breast cancer tissue by immunohistochemical method using polyclonal rabbit antibodies. The cytoplasmic staining was found in different cell types, but the most intensive specific staining was found in malignant cells and it was stronger (P < 0.01) in postmenopausal patients than in patients of reproductive age.