Water stain right side of display slowly migrating inward from edge?

Appears to be a water stain growing larger over time as it inches in from the left side of display. The stain runs from top to bottom of screen. Stain is there when monitor is off. This monitor has never been moved, never been near water or high humidity. Any ideas how to open case and clear this distracting blemish? Terrible for a $1,000 monitor.