Introduction: Congenital brain tumours are a rare entity that is nowadays often already recognised during pregnancy by ultrasound (US) and magnetic resonance (MR). Even though the definitive diagnosis is usually achieved by means of histological studies, in some cases the diagnosis may remain uncertain because of the malformative origin of this type of tumour.
Case report: We describe a patient with a diffuse congenital intracranial mass diagnosed by intrauterine US and foetal MR performed to further evaluate the lesion and the associated foetal hydrocephalus. After delivery by caesarean section, an endoscopic biopsy was performed. Several specimens were obtained and resulted in the diagnosis of primitive neuroectodermal tumour (PNET). Despite polychemotherapy, the tumour continued to enlarge and the patient died at 2 months of age. Post-mortem histological examination of the intracranial mass showed a diffuse intracranial teratoma.
Conclusion: Endoscopic biopsy specimen examination resulted in a diagnosis that was not confirmed by post-mortem findings. The scarce differentiation of teratoma components and their high variability in histomorphology as well as the huge size of the tumoral mass may limit the interpretation of endoscopic biopsy specimens, even when multiple and obtained from different areas.