Nipple inversion is the inward dimpling or retraction of the nipple-areolar complex, which may be congenital, physiologic, or pathologic. Symptoms range from cosmetic concern alone to indicators of underlying malignancy. Accurate classification (grades I–III) and recognition of associated features guide appropriate imaging and surgical management.

1. Cosmetic deformity
   Visible inward folding that may be intermittent (grade I) or permanent (grades II–III), producing an umbilicated or slit-like appearance.
2. Difficulty with lactation
   Inability to achieve effective latch; milk stasis and cracked epithelium increase the risk of mastitis and painful fissures.
3. Nipple-areolar hygiene impairment
   Moisture trapping fosters maceration, malodour, and recurrent bacterial or candidal infection.
4. Spontaneous or provoked discharge
   Serous, serosanguinous, or blood-stained secretion suggests duct ectasia, intraductal papilloma, or carcinoma; cytology is mandatory.
5. Associated mass or skin changes
   Recent onset with palpable subareolar nodule, peau d’orange, or eczematous erosion mandates exclusion of Paget disease or invasive carcinoma.
6. Pain or tethering
   Persistent pulling sensation or fixation to chest wall indicates fibrotic shortening of lactiferous ducts or malignant infiltration.
7. Grading classification
   Grade I: nipple easily everted manually and maintains projection.
   Grade II: can be pulled out but promptly retracts.
   Grade III: cannot be everted; ducts are fibrotic and shortened.
8. Sudden onset after 40 years
   New inversion, especially if unilateral and accompanied by bloody discharge, is considered malignant until proven otherwise and requires triple assessment.