Epidemiology of breast cancer. Breast cancer in women accounts for 33% of women's cancers in France. The average age at diagnosis is 63 years old. Except for women aged 55 to 65, an increase in incidence is observed from 2010 to 2018 for women younger than 40 who are not involved in breast cancer screening, as well as for women of other age groups. Age remains an important risk factor for breast cancer. The incidence rates are highest for women aged 70 to 74 (420/100 000) with also the highest increase in incidence from 1990 to 2018 (+ 1.9% per year on average). At the same time, mortality has decreased in this age group (-0.8% per year on average). However, the 5-year net survival rate is significantly lower (76%) for women over 75 than for the youngest.