Lcd back light issue ?

Hi all,

I have an issue with my screen, it doesn't seem like a dead or stuck pixel and I cannot find out what it really is.

I have not been able to take a good picture of it with a camera so I going to describe it.

In the middle of the screen, there is this "rounded" zone of around 5x5 pixels in term of size at first guess, which is brighter than the rest of the screen, it is also a little blurry on the sides.
Although, the brightness of this zone faints with the darkness of the color behind it, I mean that when the image is white we can see the zone having a brighter white, same thing for the blue/grey for example, as for the black and dim colors we do not see it anymore.
It also seem to be somewhat in another 'layer' of the screen because when I change the contrast or brightness of the screen within Windows, the zone does not change a bit.

As for the screen, it is a WUXGA laptop screen (17", 19*x12*).

PS: We can see it a little bit on the top right corner of the pict attached, on blue color. It is a bit far from what I really see, camera's fault, but it gives an overview.