PGR and breast cancer: Significantly raised risks have been reported for ER-positive,16,34,35,45 ER-negative,46 PR-positive,16,34,35,45 HER2-positive,35 HER2-negative,45 and lobular34 breast cancer sub-types in particular among pre-menopausal women14,16,34,35 but we did not find any significantly raised risks in pre-menopausal women, overall or by sub-type.