Embryonal Tumors

An embryonal tumor is a type of brain tumor made up of fast-growing cells that are left over after fetal development (embryonic cells).

Embryonic cells have an important function during the early stages of fetal development in the uterus. They help form a human body. Sometimes, extra embryonic cells remain in your child’s brain after birth. This leads to the formation of embryonal tumors.

These tumors affect children and can be cancerous (malignant) or noncancerous (benign). Most develop in the brain and some form along the spinal cord. These tumors can spread through fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Many malignant types are aggressive and can be life-threatening.

You may hear your child’s healthcare provider refer to embryonal tumors as embryomas. In the past, providers called this type of tumor a primitive neuroectodermal tumor (PNET).

What are the types of embryonal tumors?

Embryonal tumors are grouped into different tumor types. The most common type of embryonal tumor is a medulloblastoma. It develops in the cerebellum, which is the lower back part of your child’s brain.

Other non-medulloblastoma embryonal tumors of the central nervous system include:

• Atypical teratoid/rhabdoid tumor (AT/RT): It develops in the cerebellum (back of the brain).
• Embryonal tumor with multilayered rosettes (ETMRs) either C19MC-altered or NOS (not otherwise specified): It develops in the cerebrum or the front and top of the largest part of the brain and in the spinal cord.
• Medulloepithelioma: It forms in the brain, spinal cord and nerves outside of the spinal column. These aggressive, fast-growing tumors occur most often in very young children, with a poor prognosis.
• Central nervous system neuroblastoma: It forms in the layers of tissue that cover the brain and spinal cord and in cerebrum nerve tissue.
• Cribriform neuroepithelial tumor: It forms in the fluid-filled cavities (ventricles) of the brain.

• How common are embryonal tumors?

  Embryonal tumors make up an estimated 12% of all brain tumors in children from birth to age 14 in the United States. Among these, the most common, medulloblastoma, accounts for over 68% of all embryonal tumors. Atypical teratoid/rhabdoid tumors account for 17%.

  These tumors are most common among babies and children. They can affect adults but it’s rare. For example, atypical teratoid/rhabdoid tumors affect more children assigned male at birth younger than 3 years old. Embryonal tumors with multilayered rosettes are more common among children assigned female at birth younger than 4 years old.