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Despite their rarity, PIK3CAmutations in meningiomas have raised interest as potentially targetable, ubiquitous mutations owing to their presence in sporadic benign and malignant tumors but also in hormone-related cases. Using new genetically engineered mouse models, we here demonstrate that Pik3camutations in postnatal meningeal cells are sufficient to promote meningioma formation but also tumor progression in mice. Conversely, hormone impregnation, whether alone or in association with Pik3caand Nf2mutations, fails to induce meningioma tumorigenesis while promoting breast tumor formation. We then confirm in vitro the effect of Pik3camutations but not hormone impregnation on the proliferation of primary cultures of mouse meningeal cells. Finally, we show by exome analysis of breast tumors and meninges that hormone impregnation promotes breast tumor formation without additional somatic oncogenic mutation but is associated with an increased mutational burden on Pik3ca-mutant background. Taken together, these results tend to suggest a prominent role of Pik3camutations over hormone impregnation in meningioma tumorigenesis, the exact effect of the latter is still to be discovered.