Colloid Cyst

Colloid cysts are rare benign intracranial tumors most commonly found in the third ventricle, but also in the subarachnoid spaces and within the brain parenchyma. Many names have been proposed depending on their location, such as neuroependymal cyst, ependymal cyst, glioependymal cyst, choroid plexus cyst and epithelial cyst. From the neuroradiological point of view two forms have been described: a “solid” form with a compact round mass that is iso-hyperdense in CT and slightly hyperintense in T1W and highly hypointense in T2W MR images, and a “cystic-solid” form, characterised by a peripheral fluid collection surrounding a solid central core. This report describes the modifications of a solid form in a cystic-solid cyst, not previously described in the literature, and its evolution after neurosurgical drainage of the fluid collection. Some pathogenetic hypotheses on intracystic fluid production are discussed and displacement of the central solid core inside the cyst is shown.