I've had a dark brown freckle on my shoulder for years, oval about 3/16th of an inch long, it never changed until suddenly the dark skin peeled off last week and it's now just about skin color and still slightly raised as before. Is this a source of concern? I did spent a couple of days at 8,000' altitude just before that, is this just the result of sunburn ?

My copay to my general physician is $15, don't bother to answer. Thanks.