ESR1 and meningioma: These include the frequent presence of progesterone and estrogen receptors in the meningioma tissue (2–7), the possible association with tumors of the female system (8–10), the documented changes of the meningioma biology during the menstrual cycle and pregnancy (11–13), the sometimes reported regression after delivery (14), the in vitro proliferation of meningioma cell lines in culture after exposure of estrogen and progesterone (15, 16).