question: The term PROS (PIK3CA-Related Overgrowth Spectrum) indicates a wide spectrum of overgrowth disorders related to somatic mutations in PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) pathway. We present three cases with PIK3CA mutation and clinical characteristics encompassing MCAP (megalencephaly-capillary malformation) condition but lacking all criteria to a certain diagnosis, most of all showing prevalent and peculiar involvement of cerebellar structures at MRI (magnetic resonance imaging) mainly consisting in cortical rim thickening and abnormal orientation of folia axis. These cases expand the spectrum of intracranial MRI features in PIK3CA disorders.