Hormones play a causative role in the development of benign breast disease.
Vast majority of breast lesions are benign.
Postmenopausal women receiving estrogens for more than 8 years have an increased prevalence of benign breast disease by a factor of 1.7.
Use of tamoxifen associated with a 28% reduction in benign breast disease prevalence.
Genetic heterozygosity, manifested by deletions of small segments of DNA, common in benign breast disease.
Lesions frequently multifocal with each lesion demonstrating loss of heterozygosity in different areas of DNA.
There is high frequency of multiple benign or malignant lesions in the breasts of women with BRCA1 or BRCA2 gene mutations.
Noncyclic breast pain suggests cyst or mastitis.
Incidence begins to rise during the second decade of life and peaks in 4th-5th decades, as opposed to malignant diseases for which the incidence increased after menopause.