RANK/RANKL has been positively associated with ER/PR-negative BC in clinical samples, both in terms of mRNA expression levels (which were about threefold higher than in ER/PR-positive BC) and presence of RANK protein by IHC (present about three times more often (60–72%) than in ER+/PR+ BC [88,89,90,91]). Here, PGR is linked to breast cancer.