What is a benign overgrowth and thickening of the epidermis called?

A benign overgrowth and thickening of the epidermis is called acanthosis nigricans. It is a skin condition that is characterized by dark, velvety patches of skin that are typically found in the creases of the neck, armpits, and groin. Acanthosis nigricans is often a sign of an underlying medical condition, such as obesity, diabetes, or cancer.