Molecular-Genetic and In Silico 3D Characterization of an Adamantinomatous Craniopharyngioma, the ‘Chameleon’ Among Pediatric Brain Tumors

Background: Adamantinomatous craniopharyngiomas (ACPs) are congenital brain tumors that affect children and adults. Due to their location within the brain and their adhesion to surrounding structures they are difficult to treat. They are commonly associated with pituitary and hypothalamic dysfunction. The aim of this report is a detailed phenotypic and genotypic evaluation of a girl with ACP.Methods: Laboratory blood tests and magnetic resonance imaging (MRI) were performed. Histopathological investigations included staining with hematoxylin and eosin (H&E), and various antibodies. Genetics and bioinformatics tests comprised single nucleotide polymorphism (SNP) array, deoxyribonucleic acid (DNA) methylation array, next generation sequencing (NGS) and structural modeling of b-catenin.Results: An 8.5-year-old girl presented to her general practitioner with gastrointestinal symptoms and was comprehensively investigated by a paediatric gastroenterologist. During the following 1.5 years she showed traits of sensory processing disorder and complained of mild headaches. Brain imaging revealed an adamantinomatous craniopharyngioma which was surgically removed. Sequencing of the CTNNB1 gene demonstrated a tumorigenic variant, c.98C>G p.(Ser33Cys). Three-dimensional modeling of the Ser33Cys b-catenin variant indicated a weaker interaction with β‑TrCP1 (β-transducin repeat containing E3 ubiquitin protein ligase 1), due to the impossibility to undergo phosphorylation at Ser33, leading to impaired b-catenin ubiquitination, a possible cause of protein accumulation and tumorigenic progression.Conclusion: Pediatric ACP patients present with a wide range of symptoms which often results in diagnostic delay. No reliable biomarker exists for this disease, and magnetic resonance brain imaging is the investigation of choice. Next generation sequencing (NGS) is the preferred genetic test to identify the underlying somatic pathogenic variant. Overall, three-dimensional structural modeling suggests a mechanistic explanation for the pathogenicity of the CTNNB1 p.Ser33Cys variant by disruption of β-TrCP1 recognition and consequent impairment of β-catenin degradation.