For the breast cancer subtypes that did not express sex hormone receptors we found non-significantly elevated risks for work schedule involving night/rollover shift compared with day work only (HR 1.53, 95% CI 0.50 to 4.72 for ER-negative tumours; HR 1.69, 95% CI 0.58 to 4.87 for PR-negative tumours; HR 2.22, 95% CI 0.58 to 8.51 for ER-negative and PR-negative and HER2-negative tumours) (table 4). Here, PGR is linked to neoplasm.