Tumours arising at the base of the brain can interfere with hormonal function and vision. We want to describe the features of a rare group of such tumours that share a distinct marker, called TTF- 1, which suggests that they may have a common origin. Specifically, our study aims to define the genetic relationship between the tumours that have this unifying molecule – do they share a genetic make-up, or are there distinctive features? Currently, treatment of these tumours relies on surgery; no specific drug is available. We hope our study will (1) help to define better these tumours and as a result (2) point to genetic events that drive their make-up, which may offer new targets for therapy. The tumours are rare; this is why we request help from Brain UK, so we can study as many samples as possible. The results will be published.