Education
About Granulomatous Mastitis
A rare, non-cancerous inflammatory breast disease — and what current research tells us about it.
What Is Granulomatous Mastitis?
Granulomatous Mastitis (GM), often called Idiopathic Granulomatous Mastitis (IGM), is a chronic inflammatory condition of breast tissue characterized by granuloma formation around breast lobules. It is considered rare and is most often diagnosed in women of childbearing age, frequently after pregnancy or breastfeeding.
Is It Cancer?
No. Granulomatous Mastitis is not breast cancer. However, it often mimics inflammatory breast cancer on physical examination and imaging studies, which is why a tissue biopsy is usually required to confirm the diagnosis and rule out cancer and infection.
Who Does It Affect?
GM most commonly affects women in their reproductive years, often within several years of pregnancy. It can occur in women who have never been pregnant, and rarely in men. Reported cases span many ethnic backgrounds and geographies.
Possible Causes
Researchers continue to investigate the cause of GM. Current theories include:
- Autoimmune responses
- Hormonal factors
- Pregnancy and breastfeeding history
- Localized inflammatory reactions
- Bacterial involvement, particularly Corynebacterium species
- Genetic and environmental factors
No single cause has been proven, and most cases are classified as idiopathic.