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.
The strength of the family history of breast cancer, available for 4808 women, was a risk factor that was independent of histologic findings. No increased risk was found among women with no family history and nonproliferative findings. In the first 10 years after the initial biopsy, an excess of cancers occurred in the same breast, especially in women with atypia." It is not well understood whether the lesions are precursors of breast cancer or only an indication of increased risk, for most types of lesions the chance of developing breast cancer is nearly the same in the affected and unaffected breast (side) indicating only coincidence of risk factors. For atypical lobular hyperplasia there is high incidence of ipsilateral breast cancers indicating a possible direct carcinogenetic link. Epidemiology
The estimated prevalence of fibrocystic breast changes in women over their lifetime vary widely in the literature, ranging from 30 to 60% over about 50 to 60% to about 60 to 75% of all women.The condition is most common among women between 30 and 50 years of age. Terminology
In ICD-10 the condition is called diffuse cystic mastopathy, or, if there is epithelial proliferation, fibrosclerosis of breast. Other names for this condition include chronic cystic mastitis, fibrocystic mastopathy  and mammary dysplasia. The condition has also been named after several people (see eponyms below). Since it is a very common disorder, some authors have argued that it should not be termed a "disease", whereas others feel that it meets the criteria for a disease.