dulloblastoma (muh-dul-o-blas-TOE-muh) is a cancerous (malignant) brain tumor that starts in the lower back part of the brain, called the cerebellum. The cerebellum is involved in muscle coordination, balance and movement.

dulloblastoma tends to spread through cerebrospinal fluid (CSF) — the fluid that surrounds and protects your brain and spinal cord — to other areas around the brain and spinal cord. This tumor rarely spreads to other areas of the body.

dulloblastoma is a type of embryonal tumor — a tumor that starts in the fetal (embryonic) cells in the brain. Based on different types of gene mutations, there are at least four subtypes of dulloblastoma.