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[0] Colloid cyst [1] Uncommon [2] Probably due to maldevelopment and most investigators favored a neuroepithelial origin. There are also evidence that favors endoderm origin. [3] Third ventricle. [4] Clinical presentations are often seen in the third to fifth decades of life. The location of colloid cyst often makes it an effective block of foramen of Monro leading to acute hydrocephalus. Its pedunculated nature, however, allows change in position easily and release of the pressure built up. As a result, they are often associated with intermittent headache. Sudden death has been well documented. Smaller cysts may remain asymptomatic. [6] The internal lining range from cuboidal, columnar, to ciliated. Mucin producing cells can be found in some cases. The cyst content is PAS(+). Rathke cleft cyst cannot be histologically differentiated from colloid cyst of the third ventricle. Clinical correlationis important. [5] 
The size varies form several millimeter to 3-4 cm. The cyst is round, unilocular and have a thin wall. After fixation, the cyst content appears as a gray hyaline substance with consistency of soft cartilage.
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