Periductal Mastitis

Section: Breast Curriculum: Curriculum, page 10

Definition

• Benign condition affecting the major breast ducts characterized by:
  • Duct dilatation
  • Retained thick secretions
  • Periductal inflammation
  • Varying degrees of fibrosis
  • ± Development of a mammary duct fistula

Incidence

• Periareolar – young woman
• Peripheral - perimenopausal women (peak age 45-50)
• Accounts 1-2% of breast clinic referrals
• No diff in lactational or pregnancy Hx

Aetiology

• Unknown
• Smoking 90% of patients; suggests smoking alters duct epithelium
  • Smoking causes damage to ducts due to
    • Toxins
    • Local ischaemia due to microvascular damage
    • Changes in the bacterial flora

Clinical

• Classically: painful subareolar mass, clinically thought to be an inflammatory process
• Pain
  • Non-cyclical
  • May be associated with inflammation (but not necessarily)
  • Antibiotics may help
• ± Nipple discharge - in 20%
  • Variable: straw / cream / green / brown / blood stained
  • Thin & watery in young; like toothpaste in older pts
  • (unilateral or) usually bilateral; 1 or multiple ducts
• Inflammatory mass
  • Usually occur at areolar margin
  • ± Overlying skin erythema
  • Non-lactational breast abscess: periareolar
• Mammary duct fistula
  • If recurrent inflammation / infection → may develop into
    • Fistula → Discharge from a distant punctum
    • May develop spontaneously / after Bx of a mass / after I+D of abscess
    • Usually seen as a sinus at edge of areola (which may be distorted by chronic inflammation) ± associated with small underlying abscess cavity
    • Squamous lining of fistula tract is probably a metaplastic response to chronic inflammation
• Nipple retraction / inversion from fibrosis and scarring

Pathology

• Sequence
  • Metaplasia (?from smoking) - from columnar to Keratinizing squamous epithelium
  • Keratin trapped in the ducts and causes dilatation
  • Eventual rupture of the duct
  • Periductal Inflammation
  • Abscess fomration
  • Drains via closest route (edge of NAC) → Mammary duct fistula
• Histology
  • Duct dilation, with normal cellular architecture – inflammation around non-dilated subareolar breast ducts.
  • May involve a single duct system
  • Involves squamous metaplasia of lactiferous ducts (? smoking-related):
    • Keratinizing squamous epithelium extends to an abnormal depth into the orifices of the nipple ducts
    • Keratin trapped in the ducts and causes dilatation → Eventual rupture of the duct → Inflammation
• Periductal inflammatory infiltrate
  • Plasma Cells
  • Lymphocytes, polymorphs, Giant cells, Granulomata
• Bacteria:
  • S. aureus & anaerobes/mixed
  • Especially anaerobes
  • Non-lactational breast abscesses
  • Secretions of women with ectasia

Investigations

• FNA often acellular; presence of Giant Cells can be diagnostic
• Younger pt: Avoid Bx and treat with Abx (flucloxacillin & metronidazole)
• Older patient: Bx often required to rule out cancer

Management

• Exclude malignancy
• Antibiotics
  • Augmentin
  • 50% of cases will resolve
• Stop smoking
• If Abscess
  • Aspiration or I&D
• If recurrent/persistent
  • Surgery
    • Definitive duct excision
      • Microdochectomy- indications: unilateral (one duct) spontaneous discharge
      • Subareolar duct excision (Central duct excision = Hadfield’s Total Duct Excision) for multiple duct discharge (or recurrent abscess)
    • Excision of fistula
      • Laying open the fistula or excision of the fistula tract, usually combined with a Hadfield’s Total Duct Excision

Prognosis / Natural Hx:

• Recurrences are common if treated with I+D alone
• Mammary duct fistula
  • In recurrent cases: a fistula tunnels under the smooth muscle of the nipple and opens onto the skin at the edge of the areola = Mammary duct fistula
  • Mammary Duct Fistula = Connection between skin and a major subareolar breast duct
  • Treatment by fistulotomy or fistulectomy AND excision of diseased ducts