Breast cancer in men.

Epidemiologic studies of breast cancer in men have provided insights into the pathogenesis and etiology of breast cancer in both sexes. Individual carcinomas from both the male and female breast are histologically indistinguishable, but histologic types of ductal origin occur relatively more frequently in men than in women, and those of lobular origin are very uncommon in men, reflecting the absence of lobular structures in the normal male breast. The same variations in incidence and mortality rates of breast cancer among countries and racial and ethnic groups that have been observed in women also occur in men, clearly indicating that the causes of these variations are not primarily risk factors related to being female. Risk of breast cancer in men increases with age, with no change in the rate of increase at the usual age of menopause; this supports the assumption that the midlife change in the rate of increase with age in women is due to the reduction in ovarian hormone production at menopause. Incidence rates of breast cancer in men have remained stable over time, suggesting that the temporal increase in rates in women is a result of either enhanced detection due to screening or changes in risk factors that are sex-specific. In men, an increase in risk of breast cancer has been associated with testicular pathology and dysfunction, and a decrease in risk has been related to high fertility, a history of prostate cancer, and exogenous androgens. These observations suggest that risk may be enhanced by low levels, and reduced by high levels, of androgens. Conversely, high estrogen levels probably increase risk of breast cancer in men, since risk has been associated with several conditions that may result in hyperestrogenism. These conditions included obesity, rapid weight gain, elevated blood cholesterol, gallstones, non-insulin-dependent diabetes, and chronic liver diseases. Studies of the role of endogenous hormones in the etiology of breast cancer in women have tended to focus on estrogens (71). These observations on breast cancer in men suggest that the relative levels of androgens and estrogens may be of etiologic importance, and that additional studies in women should include measurements of androgens. A history of breast cancer in a first-degree relative is associated with about a doubling of the risk of breast cancer in both men and women.(ABSTRACT TRUNCATED AT 400 WORDS)