What are environmental and genetic risk factors for male breast cancer?

Updated: Oct 09, 2019
  • Author: Bagi RP Jana, MD; Chief Editor: John V Kiluk, MD, FACS  more...
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Answer

Answer

Environmental and genetic risk factors for male breast cancer have been identified. Male breast cancers are reported to be associated with the following [5] :

  • Marital status (never married at higher risk)
  • Previous breast pathology
  • Gynecomastia
  • History of testicular pathology
  • Family history of breast cancer

The family history is positive for breast cancer in approximately 30% of male breast cancer cases. A familial form of breast cancer is seen in which both sexes are at increased risk for breast cancer. Familial cases usually have BRCA2 rather than BRCA1 mutations. [4] Men who inherit BRCA2 have about a 6% lifetime risk of breast cancer, which is 100-fold higher than in men without the mutation. [6]

Klinefelter syndrome is the strongest risk factor. [4] Males with the syndrome have a risk of breast cancer that approaches that of females.

Exogenous hormone therapy, such as treatment for prostate cancer, is not associated with an increased risk of male breast tumors.  No association with smoking history was reported. Meta-analysis of epidemiology of male breast cancer failed to reveal any clear association with other potential risk factors such as reproductive history, education, various diseases, or exposure to drugs. Case-control studies on this subject have been confounded by small numbers or contradictory results.  

Overall, male breast cancer shares risk factors associated with female breast cancers, especially high estrogen levels. A few transsexual (male to female) patients have been reported with breast cancer 5-10 years after initiation of estrogen therapy; however, it is not known whether these patients are at increased risk compared with non-transsexual males. [1]  Excessive estrogen levels in men may also be related to obesity, liver disease, and thyroid dysfunction. 

These epidemiologic factors, in addition to studies suggesting that men with breast cancer have elevated estriol production, indicate a relationship between male breast cancer and hormones in addition to the well-established relationship with genetics.


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