Purple spot on the back from the age of 15 What can this be?

I'm 22 years old and I've had a purple spot on my back since I was 15, what can this be?
Expert answer:

Skin lesions have their diagnosis by viewing the lesion, you can not make the diagnosis so look for a dermatologist that he will say exactly what it is but as I like to help, I think it is a purple spot on the back.

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