Transformation Versus Ascertainment Bias of a Suprasellar Lesion: A Histopathologic Conundrum of BRAF V600E Positive Papillary Craniopharyngioma Versus Rathke's Cleft Cyst with Squamous Metaplasia: A Systematic Review. This evidence concerns the gene BRAF and Papillary Craniopharyngioma.