Aetiology

Aetiology of the disease is unknown but the following factors have been known to increase the risk (1):

• oestrogen exposure/androgen insufficiency (2)
• testicular abnormalities - undescended testes, congenital inguinal hernia, orchiectomy, orchitis
• Klinefelter’s syndrome - the risk is 50-fold greater than in the general male population
• obesity - due to an increase the oestrogen-testosterone ratio
• liver cirrhosis
• exogenous oestrogen therapy
• benign breast conditions - history of breast trauma and nipple discharge
  
  
• chest wall radiation exposure and other occupational factors (chronic heat exposure) (3)
  
  
• men with a family history of breast cancer - 2.5 times the risk of developing breast cancer
  
  
• mutations in BRCA1 and BRCA2 (2)
• the association between male breast cancer and BRCA is stronger in patients with BRCA 2 mutations than in BRCA 1 mutations.
• according to estimations around 4-40% of male breast cancer patients carry a mutation in BRCA2 and in upto 4% of patients carry BRCA 1 mutations
• the life time risk for breast cancer in
  • a male BRCA2 mutation carrier is ~7% which is estimated to be 80-100 times higher than for the general population
  • a male BRCA1 mutation carrier is just over 1% (2)

The importance of gynecomastia as a risk factor for male breast cancer is unclear (3)
Reference:

• (1) Giordano SH. A review of the diagnosis and management of male breast cancer. Oncologist. 2005;10(7):471-9.
• (2) Johansen Taber KA et al.Male breast cancer: risk factors, diagnosis, and management (Review). Oncol Rep. 2010;24(5):1115-20.
• (3) Gui, G. Male breast cancer: aetiology and clinical features. Trends in Urology & Men's Health 2012 ;3: 29–31