Ser Jorah was "cured" of greyscale by Sam Tarly last weekend. A miraculous recovery, but in the books the curing of greyscale is more questionable. When a wildling "princess" meets Shireen Baratheon she insists the girl isn't "clean" and her greyscale will eventually kill her, despite people believing she's safe.
We don't know whether the wildlings have much experience medically treating with greyscale, but George R. R. Martin doesn't waste dialogue in his books for no reason. In "A Dance with Dragons," Val, the sister of Mance Rayder's wife, refuses to allow Shireen Baratheon in the same rooms as wet nurses, and calls her "the dead girl." Jon insists Shireen is cured, but Val won't believe it. Who knows where Martin plans to go with this.