Sigh!
As has been stated MANY, MANY times the bra size of someone slim will vary greatly with the bra size of a larger lady, not just in band size, but also cup size. A slim girl with the same size breasts as a larger woman will have a bigger cup size, despite the breasts being the SAME SIZE. One ex-girlfriend of mine could wear both a 36B and a 34C quite comfortably. She could even wear a 32D even though she found it a bit tight, the cups were a perfect fit for her boobs.
It's like this, if someone wears a 36B you take off 2 and add 1 to the cup size - 34C, do this again gets 32D - get it?
So someone with a 38E equates in terms of actual size to a 36F or a 34FF, or similar.
I hope I don't see this coming up again, as it is plainly obvious to me (and any women reading this), what bra sizes, cup sizes and band sizes are in relation to one another and the women who possess them.