To study the features of mucinous carcinoma and myxoidfibroadenoma of the breast on MRI.

Fourty patients with pure mucinous carcinoma and myxoidfibroadenoma confirmed by surgical pathology who underwent breast MRI from January 2010 to May 2017 in Tianjin Medical University Cancer Institute and Hospital were analyzed retrospectively, including 26 patients with mucinous carcinoma and 14 patients with myxoidfibroadenoma. By use of the Breast Imaging Reporting and Data System (BI-RADS) lexicon, an analysis of the shape, margin, infiltration to adjacent tissues, the lesion location, signal intensity in the T₁WI and fat-suppressed T₂WI, dark internal septation, the pattern of time-signal intensity curve (TIC),rim enhancement, delayed internal enhancement, the DWI signal and ADC values was performed. Qualitative data and quantitative data were compared with χ² test and independent sample t test respectively.

There were significant differences in the margin, dark internal septation, the lesion location, rim enhancement and delayed internal enhancement between mucinous carcinoma and myxoidfibroadenoma(P<0.05).The shape, signal intensity in the T₁WI and fat-suppressed T₂WI,infiltration to adjacent tissues, the pattern of TIC, the DWI signal and ADC values were not statistically significant between the two groups(P>0.05).

The combination of irregular margin, less frequent dark internal septation, rim enhancement in the early phase, delayed heterogeneous enhancement and the lesion location where was in the shallow layer of fibro-glandular tissue were significant findings for differentiation between mucinous carcinoma and myxoidfibroadenoma.

Breast neoplasms; Mucinous carcinoma; Myxoidfibroadenoma; Magnetic resonance imaging