Breast cancer is the most common cancer in women worldwide. Its occurrence in young women is rare. Worldwide, breast cancer is diagnosed in women under 35 in 5.8% of cases. The definition of a young woman is not unequivocal. Some authors define it as an age below 35, below 40-45 or even as a non-menopausal woman. Breast cancer in young women has particular epidemiological aspects, often involving a genetic predisposition. Diagnosis is often delayed in this age group. In fact, breast cancer in young women is difficult to diagnose using the usual means of investigation, particularly mammography, given the high breast density in these women. In addition, breast cancer in young women presents more aggressive clinical and anatomopathological features than in their older counterparts, notably large tumour size, high-grade tumours, vascular invasion, lymph node invasion, hormone receptor-negative tumours and overexpression of the Her2neu receptor, giving it a poor prognosis.