It is common for moles to appear on the neck, according to WebMD. The average adult displays between 10 to 40 moles, with most appearing before age 30.
Moles form when cells called melanocytes grow in clusters rather than spreading throughout the skin. Moles that appear on the neck may be common moles or atypical moles, according to The American Academy of Dermatology. Common moles have distinct edges, and are usually tan, pink or brown. Atypical moles are larger, have indistinct edges, may be more than one color, and are often asymmetrical in shape. If a mole changes shape or color or begins to itch or bleed it is best to see a doctor, advises the National Cancer Institute.