Final answer:
The most common location for an accessory nipple is along the 'milk lines' that extend from the armpit to the groin, usually just below the normal nipple.
Step-by-step explanation:
The most common location for an accessory nipple is along the 'milk lines' or 'mammary lines' that extend from the armpit through the typical breast area, down to the groin. Accessory nipples, also known as supernumerary nipples, are a benign condition and can be found anywhere along these lines, although they typically occur just below the normal nipple. They consist of mammary gland tissue and may be mistaken for moles if not properly identified.