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Given your age and how long they have been present, they are most likely BENIGN pigmentations of your vagina. The big thing we always worry about with any pigmented area is melanoma. You should have these areas checked out by a GYN doctor just to be sure there is nothing abnormal about these areas.... but again odds are very good they are simply normal pigmented spots. If any of these spots start to grow or change in color/size at all, those would be more worrisome signs that would need immediate attention.
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