Definition
- Essential:
- An embryonal tumour originating in the CNS AND
- Absence of criteria qualifying for the diagnosis of a more specific type of embryonal CNS tumour
- Desirable:
- Focal expression of neuronal markers and absence of glial markers
Microscopy
- Characterised by poorly differentiated neuroepithelial cells with a variable capacity for divergent differentiation along neuronal, astrocytic, myogenic, or melanocytic lines.
- Can have histological features overlapping those of other brain tumours, many of which have been reclassified from this group through the identification of unique molecular biomarkers.
- Poorly differentiated neoplasms composed of cells with round to oval nuclei and a high nuclear-to-cytoplasmic ratio
- Frequent mitoses and apoptotic bodies
- Homer Wright rosettes can be found
- Necrosis and vascular endothelial proliferation may also be seen
- Calcification is relatively common
Immunophenotype
- Variable expression of divergent neuroepithelial markers, including proteins associated with both glial differentiation (GFAP) and neuronal differentiation (synaptophysin, NFP, and NeuN)
- Ki-67 proliferation > 50%
- Mitoses and apoptotic bodies.
Made with Bullet