MR features to suggest microinvasive ductal carcinoma of the breast: can it be differentiated from pure DCIS?

Abstract

Background Morphologic and kinetic characteristics of breast lesions are regarded as a major criterion for their differential diagnosis in dynamic magnetic resonance imaging (MRI). However, there have not been well-reported MRI findings of microinvasive ductal carcinoma. Purpose To evaluate MRI characteristics of microinvasive ductal carcinoma of the breast and to compare MRI findings in patients with microinvasive ductal carcinoma and pure ductal carcinoma in situ (DCIS). Material and Methods Eighty-one patients with pathologically confirmed microinvasive ductal carcinomas ( n = 37) or pure DCIS ( n = 44) were included in this study. The MRI findings were analyzed without knowledge of the pathologic and conventional imaging findings. For all the lesions detected on MRI, morphologic and kinetic analyses were performed according to the Breast Imaging Reporting and Data System. For the non-mass lesions, the presence of clustered ring enhancement was also analyzed. Statistical analyses were performed using Student's t test, χ2 test, and Fisher's exact test. Results In total 35 cases of microinvasive ductal carcinoma and 39 cases of DCIS were detected on MRI. The most common and dominant MRI findings of microinvasive ductal carcinoma and DCIS were non-mass lesions with heterogeneous enhancement. However, the spiculated margin of the mass-type lesion ( P = 0.022), the segmental distribution ( P = 0.023), and clustered ring enhancement ( P = 0.006) of the non-mass-type lesion, and the enhancement kinetics showing strong initial enhancement ( P = 0.004) with subsequent wash-out ( P = 0.001) were significantly more frequent in microinvasive ductal carcinoma than in DCIS. Conclusion Non-mass lesions with segmental distribution, heterogeneous enhancement, and strong initial enhancement with a wash-out curve were the dominant MRI findings of microinvasive ductal carcinoma. Compared with DCIS, microinvasive ductal carcinoma showed more suspicious imaging characteristics. For the non-mass lesions, clustered ring enhancement was also a characteristic finding of microinvasion on MRI.