evidence: Female breast cancer has been the leading cause of global cancer incidence in recent years, with an estimated number of new cases of 2.3 million in 2020 alone1. Male breast cancer accounts for around 1% of all diagnosed cases2, though incidence and survival trends are infrequently investigated given its rarity. Whilst the incidence of female breast cancer is stabilising or decreasing in certain age groups due to earlier detection and improved treatments3, male breast cancer has been increasing from the 1980s to 2000s at least in the United Kingdom (UK) and the United States (US)4,5. [...] When examining incidence trends over time by age group, three key findings are highlighted. First is the increase in incidence over the study period for younger women (aged 18–29; and 30–39). Several possible explanations include: increasing awareness of breast symptoms leading to more women being diagnosed; but also risk factor exposures in early life such as earlier age of thelarche (pubertal phase of breast development) and menarche than previous decades22,23, leading to increased cumulative exposure to oestrogen; and increased use of hormonal contraceptives which pose an elevated risk for breast cancer24. Second, the decline in incidence for women aged 50–69 years from 2005 to 2019 may be a reflection of the success of screening programmes; and third, the decline from 2015 onwards for women aged 70–89 years coincides with the launch of the "Be Clear on Cancer" campaign aimed at women in this age group25.