huge brown patch on upper thigh

[aarya12]

i am 23 and since i was 7-8 years old i started developing a brown patch on my right thigh. it is big enough to cover part of upper thigh and contiguous region of side of waist. on the thigh it is solid brown and around the edges and waist its more like scattered small patches dispersing.

I have consulted several dermatologists about this but none could diagnose what this actually is.some said its fungal infection, others said this looks like a birthmark..(even though it wasn't there when i was born!).

i can really use some guidance. even if its not with 100% confidence.

[aarya12]

also they look more like cafe-Au-Lait but darker and on larger area, more uneven edges.