What could be causing brighter discoloration of skin on edge of lip?

[nycnight]

Have had a bright spot of skin (not a bump or pimple, just a discolored, almost glowing white spot on the skin) on the edge of my lip for a while now. I did see my dermatologist some time ago who attributed it to eczema on the skin near that spot which was making the rest of the skin seem a darker pinker tone causing this spot to seem brighter than it really is. I was given a weak steroid to apply to the skin to help with that, but there has been no change so just want some other opinions on what it could be. It has been pretty consistent for about 10 months now. I tried the steroid for the first few weeks (and actually tried it a few other times months later), "natural" moisturizers and facial washes, but seen no change in this bright spot. Any ideas on what it could be? Thanks