Mastitis is an inflammatory condition of the breast parenchyma, most frequently infectious in the lactational period and non-infectious or duct-centric in non-lactational settings. Recognition of its characteristic features permits prompt antimicrobial therapy and prevents progression to abscess formation.

1. Painful induration
   A localized, wedge-shaped area of firm, tender tissue develops rapidly, often in the upper outer quadrant. Pain is throbbing and exacerbated by movement or nursing.
2. Erythema and oedema
   Brilliant erythema with irregular borders spreads centrifugally; peau d’orange change reflects dermal lymphatic obstruction and interstitial oedema.
3. Pyrexia and systemic response
   Temperature ≥ 38.5 °C with chills, myalgia, and tachycardia indicates bacterial infection; rigors suggest bacteraemia.
4. Nipple-areolar changes
   Fissures, erosions, or milk stasis plugs serve as bacterial entry portals; retraction or persistent erythema may signal underlying duct ectasia in non-lactational disease.
5. Purulent nipple discharge
   Expressible, thick, yellow-green secretion from a single duct is typical of duct-centric or sub-areolar abscess; frank pus on aspiration confirms abscess formation.
6. Axillary lymphadenopathy
   Tender, mobile nodes < 2 cm accompany acute infection; firm, matted nodes raise concern for granulomatous or underlying neoplastic processes.
7. Abscess indicators
   Fluctuant mass, persistent fever > 48 h despite antibiotics, or leukocytosis > 15 × 10⁹ L⁻¹ signifies pus collection requiring image-guided drainage.
8. Chronic or recurrent mastitis
   Intermittent pain, peri-areolar fistula, and thick nipple discharge point to squamous metaplasia of lactiferous ducts (SMOLD) or granulomatous mastitis; biopsy excludes malignancy.