What is the cause of Idiopathic Granulomatous Mastitis (IGM)?

Causes of Idiopathic Granulomatous Mastitis (IGM)

The exact cause of Idiopathic Granulomatous Mastitis (IGM) remains unknown, but several potential etiologic factors have been proposed including autoimmune processes, infections, hormonal imbalances, and chemical reactions associated with oral contraceptive pills or lactation.

Key Etiologic Factors

• Autoimmune Response: One of the main hypotheses suggests IGM may be an autoimmune disorder, though the specific autoimmune mechanism has not been fully elucidated 1.

• Infectious Agents: Unknown microbiological agents have been suggested as potential triggers, with Corynebacteria species being particularly associated with IGM development 2.

• Hormonal Factors: Several hormonal conditions show strong association with IGM:

  • Recent pregnancy and lactation (particularly within 5 years of last lactation) 3
  • Hyperprolactinemia 3
  • Use of oral contraceptive pills 3

• Other Associated Factors:

  • Smoking has been identified as a significant risk factor 3
  • Ethnicity appears to play a role, with higher prevalence among Hispanic women, particularly those of Mexican origin 2
  • α1-antitrypsin deficiency has been suggested as a potential contributing factor 4

Clinical Presentation

• Most common presentation is an unilateral, discrete breast mass 4
• Other presentations include:
  • Nipple retraction 4
  • Sinus formation with inflammation of overlying skin 4
  • Breast pain or painful mass 2
  • Suppuration 2
  • Suspicious imaging findings that can mimic malignancy 2

Diagnostic Considerations

• IGM is a diagnosis of exclusion that requires ruling out:

  • Breast malignancy 5
  • Specific granulomatous mastitis with identifiable causes 2
  • Infectious etiologies 5

• Over 50% of IGM cases may have suspicious BI-RADS scores on imaging, making differentiation from malignancy challenging 2.

Treatment Approaches

• Treatment remains controversial with multiple approaches:

  • Corticosteroids (often first-line therapy) 3
  • Non-steroidal anti-inflammatory drugs (NSAIDs) 2
  • Antibiotics (particularly when infection is suspected) 2
  • Surgical interventions including incision and drainage or lumpectomy 2
  • Observation alone may be appropriate in some cases 2
  • Immunosuppressive agents like methotrexate for refractory cases 2

• Recurrence is common, reported in approximately 5-20% of cases despite treatment 3, 5.

High-Risk Demographics

• Young females of reproductive age, particularly:
  • Those within 5 years from their last lactation 3
  • Hispanic women, especially of Mexican origin 2
  • Women with history of breastfeeding 3
  • Smokers 3
  • Women with hyperprolactinemia 3
  • Women who have used oral contraceptive pills 3

IGM presents significant diagnostic and therapeutic challenges due to its ability to mimic malignancy and its often chronic, relapsing course. A multidisciplinary approach involving surgeons, radiologists, and pathologists is essential for proper diagnosis and management.