ESR1 and breast cancer: Approximately 88% of meningiomas express progesterone receptors (PR), but only 30% express estrogen receptors (ER).58,59 The ER is expressed in 70% of breast cancers; the PR is expressed in 50% of ER-positive breast cancers but is rarely seen in ER-negative breast cancers.60,61,62,63 However, the studies by Criscitiello et al10 and Lopez-Rivera et al8 did not find any significant association between the hormonal receptor status of breast cancer and the risk of meningioma.