PGR and Anaplastic (Malignant) Meningioma: The malignant meningioma IOMM-Lee cell line [28] was the second line selected from the nervous system because over 70% of meningiomas express PR [29], and clinical trials conducting long-term MF treatment of patients with unresectable meningioma have been promising [30,31]; yet the expression of PR in IOMM-Lee was, to our knowledge, unknown.