Skin changes are the signs of acanthosis nigricans. The commonly affected areas include the sides and back of the neck, under the arms (axillae), the groin, and the anal/genit. In some cases, other body folds may also be involved, such as behind the knees, in front of the elbows, under the breasts, and the navel region. There are few reports in which almost all of the skin is affected. Changes in skin occur slowly and there is the possibility of odor or itch in the affected skin.