Other CNS embryonal tumours

Other CNS embryonal tumor, was introduced in the WHO 2016 classification of CNS tumors. Some of these tumors of this category has been previously designated as CNS-PNET but this terminology has been abandoned.

Other CNS embryonal tumours
Diagnosis in short
Other CNS embryonal tumorH&E stain.
Synonyms	CNS-PNET
LM DDx	small round blue cell tumours
IHC	S-100 +ve, Syn +/-ve
Site	brain, spinal cord
Prevalence	rare - typically in children and young adults
Prognosis	poor (WHO Grade IV)

General

Other CNS embryonal tumours are a group of primitive neuroeptithelial tumors that are to be classified in distinct molecular groups in the future. Currently it is a exlcusion criteria encompassing four subgroups

• CNS neuroblastomas
• CNS ganglioneuroblastomas.
  • often characterized by FOXR2 fusions: CNS neuroblastoma with FOXR2 activation (NB‐FOXR2)
• CNS medulloepithelioma.
  • but absence of C19MC alteration, otherwise classified as ETMR
• CNS embryonal tumour, NOS
  • Similarities to astroblastoma: High‐grade neuroepithelial tumours with MN1 alteration (HGNET‐MN1)
  • NUTM1-positive IHC: Ewing's sarcoma family tumour with CIC alteration (EFT‐CIC)
  • BCOR-positive IHC: HGNET BCOR‐altered neuroepithelial tumours

IHC

CNS Ganglioneuroblastoma + Neuroblastoma

• Syn -/+ve.
• Vim -ve.
• GFAP usu -ve.
• MIB-1 usu high.

Medulloepthelioma

• Syn +/-ve.
• NF +/-ve.
• GFAP usu -ve.
• CK may be focally +ve.

DDx:

• AT/RT
• ETMR
• Anaplastic ependymoma
• H3F3A G34-mutated Glioblastoma