RB1 and ductal breast carcinoma in situ: Previous in vitro studies in the literature had suggested progesterone induces invasiveness of BCa cells principally via PR-B [29, 30] although clinical observations noted more frequent elevation of PR-A in ductal carcinoma in situ (DCIS) and invasive breast lesions [23] and associated PR-A rather than PR-B with lower DFS [24].