Symptoms follow a periodic trend closely tied to the menstrual cycle. Symptoms tend to peak in the days to weeks before each period and decrease afterwards. At peak, breasts may feel full, heavy, swollen, and tender to the touch. No complications related to breastfeeding have been found. Pathophysiology
The exact mechanism of the condition is not fully understood, though it is known to be tied to hormone level fluctuation, the condition usually subsides after menopause and is closely related to the menstrual cycle. Post-menopausal under hormone replacement therapy have also reported symptoms of fibrocystic breast changes indicating hormones may play a major role. This condition is an accumulative process, partly caused by the normal hormonal variation during a womans monthly cycle. The most important of these hormones include: estrogen, progesterone and prolactin. These hormones directly affect the breast tissue by causing cells to grow and multiply. Other hormones such as TSH, insulin, growth hormone and growth factors such as TGF-beta exert both direct and indirect effects by amplifying or regulating cell growth. Chronic hormonal fluctuations eventually produce small cysts and/or areas of dense or fibrotic tissue over the years. By the age of 30, multiple small cysts and breast pain may arise. Larger cysts usually do not occur until after the age of 35. Over time, presumably driven by aberrant growth signals, such lesions may accumulate epigenetic, genetic and karyotypic changes such as modified expression of hormone receptors and loss of heterozygosity.
A possible complication arises through the fact that cancerous tumors may be more difficult to detect in women with fibrocystic changes. Breast cancer risk
Breast cancer risk is elevated in a defined fraction of the lesions. Except for people with a strong family history of breast cancer, where the risk is two-fold, nonproliferative lesions have no increased risk. Proliferative lesions also have approximately a two-fold risk. In particular, atypical hyperplasia which is associated with an increased risk of developing breast cancer. Theres two types of atypical hyperplasia: lobular and ductal; the lobular type is associated a greater cancer risk of approximately 5-fold and especially high relative risk in premenopausal women. Atypical ductal hyperplasia is associated with 2.4-fold risk. In contrast, a New England Journal of Medicine article  states that for women with a strong familial history of breast cancer, the risk of future breast cancer is roughly doubled, independent of histological status. The article further states "The relative risk of breast cancer for the cohort was 1.56 (95 percent confidence interval, 1.45 to 1.68), and this increased risk persisted for at least 25 years after biopsy. The relative risk associated with atypia was 4.24 (95 percent confidence interval, 3.26 to 5.41), as compared with a relative risk of 1.88 (95 percent confidence interval, 1.66 to 2.12) for proliferative changes without atypia and of 1.27 (95 percent confidence interval, 1.15 to 1.41) for nonproliferative lesions.