Nomenclature changes
Removal of the term primitive neuroectodermal tumour
- Through molecular profiling Sturm et al. discovered four new CNS tumour types which have been previously described under the category of primary neuroectodermal tumours of the CNS
- CNS Ewing sarcoma family tumor with CIC alteration
- CNS high-grade neuroepithelial tumor with MN1 alteration
- CNS neuroblastoma, FOXR2-activated,
- CNS tumour with BCOR internal tandem duplication (CNS tumour BCOR ITD)
CNS embryonal tumour with rhabdoid features
- Old WHO 2016 classification
- Now re-classified as Atypical teratoid/rhabdoid tumour (AT/RT)
- Definition
- A highly malignant CNS embryonal tumour composed predominantly of poorly differentiated elements and including rhabdoid cells, either with expression of SMARCB1 (INI1) and SMARCA4 (BRG1) or in which SMARCB1 and SMARCA4 status cannot be confirmed.
- Histology
- In CNS embryonal tumour with rhabdoid features, neoplastic cells demonstrate histological and immunohistochemical evidence of polyphenotypic differentiation along neuroectodermal, epithelial, and mesenchymal lines.
- Thus, the pathological features of these tumours are the same as those for AT/ RTs.
- Because of the extreme rarity of CNS embryonal tumour with rhabdoid features, no data are available to determine whether its epidemiological or clinical characteristics are significantly different from those of AT/RTs.
- CNS WHO grading
- Grade 4
Other CNS embryonal tumours
General
- These were from the old WHO 2016 Classification
Definition
- A group of rare
- Poorly differentiated embryonal neoplasms of neuroectodermal origin
- That lack the specific histopathological features or molecular alterations that define other CNS tumours.
Localisation
- Cerebral hemispheres
- Rare
- Brainstem and spinal cord
Numbers
- 1% of brain tumours overall
- 13% of neoplasms arising in children aged 0-14 years
- 3-5% of all paediatric brain tumours (< 18 years)
- Incidence of adult CNS embryonal tumours is difficult to determine because of their rarity and lack of signature biomarkers
Cell origin
- Primitive neuroepithelial cells
Radiological
- All types of embryonal tumours look similar on imaging
- Solid masses +/- cystic or necrotic areas
- CT:
- -C: isodense to hyperdense
- +C: Density increases
- 60% have calcification
- MRI: do not have extensive oedema
- T1: hypointense relative to cortical grey matter
- T2:
- Similar intensity to grey matter
- Cystic or necrotic areas are hyperintense.
- Haemorrhage: hypointense
- T1+C:
- Contrast enhancement
Histopathology
Macroscopy
- Well-circumscribed pink masses,
- Demarcation between tumour and brain ranges from indistinct to clear cut.
- Mainly solid
- Can be also necrotic and haemorrhagic areas
- Soft unless they contain a prominent desmoplastic component, in which case they are firm and often have a tan colour
Microscopy: histological subtypes
- Medulloepithelioma
- A CNS embryonal tumour with a prominent pseudostratified neuroepithelium that resembles the embryonic neural tube in addition to poorly differentiated neuroepithelial cells
- External limiting membrane has a periodic acid-Schiff-positive
- Luminal surface lacks cilia and blepharoblasts
- No C19MC alterations
- Immunophenotype
- Positive
- LIN28A is expressed by medulloepitheliomas that lack C19MC amplification
- Patchy positive
- Cytokeratins
- Negative/Rare positive
- Neuronal markers: Synaptophysin, NFPs, GFAP-positive tumour
- EMA
- Ki67 high
- CNS neuroblastoma
- A CNS embryonal tumour characterized by
- Poorly differentiated neuroepithelial cells,
- Groups of neurocytic cells,
- A variable neuropil-rich stroma
- Architecture features
- Homer wright rosettes
- Palisading patterns of cells
- Regions of necrosis with granular calcification.
- Immunophenotype
- Embryonal cells (neuroepithelial cells)
- Negative
- Neural markers: synaptophysin, GFAP
- Neurocytic cells
- Positive
- Neural markers: synaptophysin, GFAP
- Ki67
- High in embryonic cells
- CNS ganglioneuroblastoma
- A CNS embryonal tumour characterized by poorly differentiated neuroepithelial cells and groups of neurocytic and ganglion cells.
- Ganglion cells
- Binucleated
- Normally in small groups among the embryonal cells.
- Architectural features
- Homer Wright rosettes,
- Palisading patterns of cells,
- Regions of necrosis with granular calcification
- Immunophenotype
- Embryonal cells
- Negative
- Neural markers (synaptophysin)
- Glial markers (GFAP)
- Groups of neurocytic and ganglion cells
- Positive
- Synaptophysin,
- NFPs,
- MAP2, and
- NeuN
- Ki-67 high in embryonal cells,
- Lower elsewhere
Prognosis
- Very poor prognosis, with multiple local relapses and widespread leptomeningeal dissemination
- 5 yr survival
- 40%, poorer than the survival rate for children with medulloblastoma
- Poor prognostic factors
- Young age
- Metastatic disease
- Incomplete resection
- 25-35% Metastatic dissemination
- Mostly in the subarachnoid space, including the spinal canal.
- Diagnostic lumbar puncture for cytology, as well as spinal MRI, is mandatory for all patients
- Rare:
- Extraneural metastases to the bone, liver, and cervical lymph nodes
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