A mole, or “nevus”, is a common benign skin growth composed of pigment cells called melanocytes. The number of moles you develop is dependent on your genes, and cumulative sun exposure. A dermatologist is a specialist in determining whether a mole is harmless or of concern.
Typically, this is done by visual examination although frequently a tool called a dermatoscope is used as well. If a mole appears atypical a biopsy is generally performed.