Embryonal tumours develop from cells that are left over from the earliest stages of our development, while we are still growing in our mother's womb as an embryo. (Previously called Primitive Neuro-Ectodermal Tumours or PNETs)
Embryonal tumours occur in the brain or the spine, and can be divided roughly into supratentorial tumours and infratentorial tumors. This means above or below the tentorium – a membrane which separates the cerebellum from the lobes of the brain.
The infratentorial embryonal tumours are far more common than the supratentorial embryonal tumours. Infratentorial embryonal tumours include medulloblastomas (which develop in the cerebellum) and pineoblastomas (which develop in the pineal region of the brain). Supratentorial embryonal tumours include ETMRs.
They are more common in children and young adults. About 20-25% of childhood brain tumours are embryonal tumours, which are high grade, fast growing tumours.
Embryonal tumours occur most frequently in younger children and incidence decreases with age with more than half being diagnosed in children less than 10 years old.
Nearly three-quarters (73%) of embryonal tumours are medulloblastomas.
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