Nipple Types: Protruding, Retracted, Inverted, and Supernumerary

Nipple morphology varies widely among individuals. Understanding the different types helps normalize anatomical diversity and identify when clinical evaluation may be warranted.

Primary Types Based on Projection

1. Protruding (Erectile): Projects outward at rest or with stimulation. This is the most common type and facilitates infant latch during breastfeeding.
2. Retracted (Flat): Lies flush with the areola but may evert with stimulation or cold exposure. Can make initial latch challenging but is often manageable with support.
3. Inverted: Retracted inward due to shortened lactiferous ducts or fibrosis. Graded 1–3 (mild to severe non-protractility). May impede breastfeeding; interventions include the Hoffman technique, nipple shields, suction devices, or surgical correction.

Supernumerary (Accessory) Nipples

• Develop along the embryonic milk lines extending from axilla to groin
• Usually small and non-functional, though they may rarely lactate
• Can be removed for cosmetic reasons if desired

Clinical Notes

• Sudden inversion in adulthood warrants evaluation for an underlying mass
• Piercing, trauma, or surgery can alter projection
• All types represent normal anatomical variations unless symptomatic or representing a new change