In both normal and malignant breast tissues, progesterone can be metabolised into 5α-pregnanes and 4-pregnenes by 5α-reductase and 3α-hydroxysteroidoxidoreductase enzymes.44 Interestingly, we observed some tumours with detectable ER by immunohistochemistry and PR-B by PLA that showed no evidence of interaction by PLA. Here, RB1 is linked to neoplasm.