What is a colloid cyst and are they dangerous? Colloid cysts are generally slow-growing, non-cancerous brain tumours located in the third ventricle, a fluid-filled cavity in the centre of the brain.

This structure was a cystic extension of the cavum veli interpositi (CVI), which is a narrow CSF-filled space between the lateral ventricles, inferior to the fornices, and superior to the third ...