Breast cancer is a malignant tumour that originates in the breast tissue. Most breast cancers are invasive tumours that have grown beyond the ducts or lobules of the breast and can metastasize to other parts of the body through the bloodstream and the lymphatic system.

Breast cancer is very common in women but rare in men, with less than 1% of cases diagnosed in men. There is a racial difference in breast cancer cases in men compared with women in the US. While breast cancer cases were slightly higher in white women compared with black women, black men had a considerably higher rate of incidence than white men. According to a December 2019 study by Sung and colleagues published in JNCI Cancer Spectrum, the incidence was higher in black men for all breast cancer types, such as hormone-positive, hormone-negative, and triple-negative breast cancer.

The researchers analysed breast cancer cases between 2010 and 2016 from the SEER database in the US and found that cancer was 52% higher in black men than white men, whereas among women, rates were 2% higher in white women than in black women. The reason for this difference is largely unknown, but researchers have speculated there may be a number of genetic and non-genetic risk factors such as gene mutations, biomarkers and radiation exposure.

The numbers of breast cancer cases in men are growing steadily in the US. GlobalData epidemiologists forecast an increase in the diagnosed incident cases of breast cancer in men in the US from 2,300 cases in 2018 to 2,550 cases in 2028, at an annual growth rate (AGR) of 1.10%. Although this cancer is rare in men, the burden is disproportionally higher in black men.

Breast cancer has been poorly researched in men. There is also a distinct lack of awareness, as well as a social stigma, in seeking early diagnosis and treatment of breast cancer, which is predominantly associated with women. Thus, breast cancer in men is usually diagnosed late, with poor survival outcomes. Effective public health strategy is needed to overcome apathy and social stigma regarding male breast cancer. Researchers should also explore the causes of racial differences in breast cancer.