The expression of 17β-hydroxysteroid dehydrogenase (17β-HSD) type 1 and type 2 was examined immunohistochemically in 111 invasive ductal carcinomas, and correlated with various clinicopathological parameters. This study investigates local regulatory mechanisms of oestrogens in human breast carcinoma. 17β-HSD type 1 was immunolocalized in carcinoma cells of 68 out of 111 invasive ductal carcinoma cases (61.3%). 17β-HSD type 2 immunoreactivity was not detected in all cases examined. A significant inverse correlation was observed between the immunohistochemical expression of 17β-HSD type 1 and histological grade of the carcinoma (P < 0.02). There was a significant correlation between 17β-HSD type 1 and oestrogen receptor (ER) labelling index (LI) (P < 0.05). In addition, carcinoma cells expressing immunoreactive 17β-HSD type 1 were frequently positive for ER. 17β-HSD type 1 was also correlated with progesterone receptor (PR) LI (P < 0.05). There was a significant inverse correlation between 17β-HSD type 1 and Ki-67 LI (P < 0.0001). No significant correlations were detected between 17β-HSD type 1 and other clinicopathological parameters, including patient age, menopausal status, stage, tumour size, lymph node status and prognosis. This study suggests that 17β-HSD type 1 plays an important role in the regulation of in situ oestradiol production in hormone-dependent breast carcinomas. (C) 2000 Cancer Research Campaign.
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