That is damage from a micro fissure and the LCD liquid leaking out into the in-between layers of glass in the display panel by capillary action. It is caused by impact damage hitting the screen at the middle of the largest blob. The damage itself was not apparent at first as was not big enough to leak out immediately but when the display was shut down and closed up, the liquid started to spread out from the micro-fissure. It is a very slow process that looks like the LCD is rotting away.

I have seen this on many LCD display systems on Macs, PCs, Palm Pilots, Watches and a few calculators. Even one of my Yaseu hand-held radios had this happen to it.