Immunophenotypic features of dedifferentiated skull base chordoma: An insight into the intratumoural heterogeneity.

Chordomas are rare and low-grade malignant solid tumours, despite their histologically benign appearance, that arise in the bone from embryonic notochordal vestiges of the axial skeleton, a mesoderm-derived structure that is involved in the process of neurulation and embryonic development. Chordomas occurring in the skull base tend to arise in the basiocciput along the clivus. Three major morphological variants have been described (classical, chondroid, and atypical/dedifferentiated). The pathogenesis and molecular mechanisms involved in chordoma development remain uncertain. From a pathological standpoint, the microenvironment of a chordoma is heterogeneous, showing a dual epithelial-mesenchymal differentiation. These tumours are characterised by slow modality of biologic growth, local recurrence, low incidence of metastasis rates, and cancer stem cell (CSC) phenotype. The main molecular findings are connected with brachyury immunoexpression and activation of the downstream Akt and mTOR signalling pathways. The differentiation between typical and atypical chordomas is relevant because the tumoural microenvironment and prognosis are partially different. This review provides an insight into the recent and relevant concepts and histochemical markers expressed in chordomas, with special emphasis on dedifferentiated chordomas and their prognostic implications.

Case-based update: primary intraventricular brain abscess in a 10-year-old child.

BACKGROUND: Intraventricular abscesses are very rare and usually result from secondary rupture of a brain abscess. In the few published cases, clinical presentation was subacute and different pathogens were found. The diagnosis might be mistaken as an intraventricular tumor. CASE REPORT: This is a case of a 10-year-old girl suffering from cyanotic heart disease that was presented with subacute onset of headache, vomiting, and some signs of inflammation. Symptoms lead to early brain imaging (CT/MRI) demonstrating left ventricular horn lesion affecting adjacent brain structures. Neuroradiologists suspected an intraventricular tumor, but cardiac history and signs of inflammation led to lumbar puncture and evidence of CNS infection, and intraventricular abscess was suspected. Navigated aspiration was performed, and multi-sensitive Eikenella corrodens was cultivated. Broad antibiotic treatment and dexamethasone were initiated, and symptoms disappeared. Follow-up imaging demonstrated gradual regression of the intraventricular abscess. The girl underwent regular professional teeth cleaning which was discussed as possible cause of infection. CONCLUSIONS: Although an isolated intraventricular abscess is a very rare event, typical predisposing cardiac history together with central nervous symptoms and an intracranial contrasting mass should always lead to the differential diagnosis of a brain abscess and be biopsied first. E. corrodens is a typical organism of the mouth flora, but a rare cause for a brain abscess. Harmless teeth cleaning procedures may cause hematogenic spread and lead to CNS infections, e.g., in patients with predisposing diseases. To our knowledge, there are only six previous reports of primary intraventricular brain abscess.