A clear role of PIK3CA in CIN may not have been uncovered to date because PI3K research has mainly focused on the analysis of bulk cell populations, using either PI3K inhibitors, experimental conditions of acute signalling often by supra-physiological doses of growth factors, and established PIK3CA mutant cells that have adapted to constitutive PI3K activation. This evidence concerns the gene PIK3CD and cervical squamous intraepithelial neoplasia.