Male breast cancer

INTRODUCTION

Male breast cancer (MBC) is rare in contrast to female breast cancer, which is the most common cancer and second leading cause of cancer deaths in women [1]. Although MBC shares many similarities with cancer of the female breast, there are also important differences [2].

EPIDEMIOLOGY

In the United States, approximately 1910 new cases of MBC are diagnosed annually, and 440 deaths occur; this represents less than 0.5 percent of all cancer deaths in men annually [1]. By contrast, in Tanzania and areas of central Africa, breast cancer accounts for up to 6 percent of cancers in men [3]. In the United States, the ratio of female to male breast cancer is approximately 100:1 in whites, but lower (70:1) in blacks [2,3]. Blacks also have a poorer prognosis, even after adjustment for clinical, demographic, and treatment factors. (See 'Racial disparities' below.)

The median age of onset of MBC is 65 to 67, approximately 5 to 10 years older than in women [2,4-9]. Like female breast cancer, the incidence of MBC has been increasing; one report suggests that incidence has increased 26 percent over the past 25 years [10].

Risk factors — Although the majority of men with breast cancer have no identifiable risk factors, several have been identified, many related to hormone levels. In a meta-analysis of published case-control studies, the risk of developing MBC was increased in men with the following characteristics: never married, Jewish ancestry, previous benign breast disease, gynecomastia, history of testicular or liver pathology, family history of breast cancer, or prior chest wall irradiation [3]. Other risk factors were identified in an analysis of data from the prospective NIH-AARP Diet and Health study, during which 121 of 324,920 (.04 percent) men developed breast cancer [11]. The risk was significantly higher in men who had a first degree relative with breast cancer (RR 1.92), a history of a bone fracture after age 45 (RR 2.2), obesity (RR 1.79) and low levels of physical activity; trends with smoking characteristics were inconsistent, and alcohol consumption was not related to risk.

Gynecomastia, which is most often drug-related (table 1), is probably not a precursor for MBC, but may be associated with it because of shared hormonal risk factors. (See "Epidemiology and pathogenesis of gynecomastia" and "Causes and evaluation of gynecomastia".)