ABSTRACT
Breast cancer is the most common malignancy in women in numerous industrialized countries, and its incidence is increasing in many countries around the world. Breast cancer is more common in elderly women with incidence increasing after the age of 40 years and especially after the menopause, but breast cancer sometimes develops in very young women, even, albeit rarely, before the age of 20. A woman’s menstrual and reproductive history may have a substantial impact on her risk of developing breast cancer. Early age at menopause, also due to oophorectomy, has been reported to be a protective factor in breast cancer. Parity, age at first childbirth, length of menstrual cycle and regularity, late menopause, breast-feeding, etc. also seem to be related to breast cancer incidence, but no factors have yet been found that can be used to prevent breast cancer or reduce breast cancer incidence. During the past decade, interest in hereditary reasons for breast cancer development has increased, especially since women with the BRCA1 and/or BRCA2 gene have been shown to have a high risk of developing breast cancer during their lifetime, especially at an early age.
