Foci on breast magnetic resonance imaging in high-risk women: cancer or not?

PURPOSE: To assess how frequently foci are identified on MRI in high-risk patients, and their association with malignancy, breast density, and background parenchymal enhancement (BPE). MATERIALS AND METHODS: In this multicentric study, two readers, in consensus, retrospectively reviewed screening breast MRI of 245 high-risk women, performed between 2009 and 2014. Eligible patients had at least two consecutive screening MRI, and a follow-up of at least 1 year after a lesion was first detected; histology was available for all suspicious findings. Breast density, BPE (both using BI-RADS lexicon), presence, and changes at follow-up for foci were evaluated. Clinical history of the patients was reviewed. Chi-square test was used to define significant correlations. RESULTS: 166 women (mean age 43 years), who underwent a median of 4 MRI (range 2–6) during the study period, were included. 68 foci were found in 58 women [34.9 %, 95 % confidence interval (CI) 28.1–42.5 %]. Foci were more frequent in dense breasts (P = 0.079) and with moderate or marked BPE (P < 0.001). During follow-up, two foci increased in size (2.9 %, 95 % CI 0.8–10.1 %) and at biopsy, a cancer was found (1 high-grade ductal carcinoma in situ, 1 tubular carcinoma). Breast cancer was diagnosed in the other three cases, not initially appearing as foci, and it was more frequent in women with dense breasts (P = 0.04); no correlation between cancer and BPE was found (P = 0.145). CONCLUSIONS: Foci are relatively frequent in screening MRI, and they are usually benign. An increase in size is the most reliable criteria to suspect malignancy.