In Barrett's oesophagus, affected cells undergo a transformation

There is a very small increased risk of developing oesophageal cancer if you have Barrett’s oesophagus. — 123rf.com

Barrett’s oesophagus is a condition in which the pink lining of your oesophagus – the long tube that connects your mouth to your stomach – is damaged by constant acid reflux from your stomach contents.

This causes the lining of your oesophagus, especially the lower part of it, to thicken and become red.