A Rathke's cleft cyst is a benign growth on the pituitary gland in the brain, specifically a mucin-filled cyst in the posterior portion of the anterior pituitary gland. It occurs when the Rathke's pouch does not develop properly and ranges in size from 2 to 40 mm in diameter.Asymptomatic cysts are commonly detected during autopsies in 2 to 26 percent of individuals who have died of unrelated causes. [Source: Wikipedia 
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