Positive association between progestins and the evolution of multiple fibroadenomas in 72 women

Objective: Multiple fibroadenomas (MFA) of the breast is a rare benign disease, thus its natural history is poorly understood. The aim of our study was to describe the radiological evolution of MFA and to evaluate the influence of different factors on this evolution. Methods: This was a longitudinal cohort study. All patients included had two clinical and radiological assessments (breast ultrasound (US) and/or MRI) at least 5 years apart. Results: Seventy-two women were followed for 7.6 +/- 2.1 years. The radiological evolution showed a decrease or stability in the number of fibroadenomas (FA) in 26/44 cases on the MRI and in 38/64 cases on the US. There was a decrease of size in 35/44 cases on the MRI and in 53/64 cases on the US. An increase in the number of FAs was found in 18/44 cases in the MRI and 26/64 cases in the US with, for the majority, a decrease of size (19/26 by MRI and 16/18 by MRI). Older age at the first FA (P < 0.0001) and at the diagnosis of MFA (P < 0.0001), pregnancy (P = 0.003) and progestin use (P < 0.001), particularly lynestrenol (P < 0.0001), had a beneficial effect on the evolution of MFA. Conclusion: This is the first longitudinal study describing women with MFA. The radiological evolution of MFA seamed favorable and similar to that expected for a single FA. We identified factors influencing the evolution of the disease, including progestin treatments such as lynestrenol, which could have a beneficial effect. Our cohort should be followed further in order to expand our knowledge of MFA, especially concerning the risk of breast cancer.