Invasive Micropapillary Carcinoma of the Breast: MR Imaging Findings

OBJECTIVE To analyze the magnetic resonance (MR) imaging findings of invasive micropapillary carcinoma of the breast. MATERIALS AND METHODS MR images were retrospectively evaluated in 14 patients (age range: 37-67, mean age: 49 years) with pathologically confirmed invasive micropapillary carcinoma of the breast. The enhancement type (mass/non-mass), shape, margin, contrast enhancement, and time-intensity curve pattern on the dynamic study were correlated with the histopathologic features. Associated findings, such as edema, nipple change, skin change and enlarged axillary lymph nodes were also studied. RESULTS The most common features of the masses were irregular shape (12 of 14 patients, 85.8%) and irregular or spiculated margin (11 of 14 patients, 78.7%). The contrast enhancement was heterogeneous in 11 patients (78.7%), rim enhancement in 2 cases (14.2%), and homogeneous in one patient (7.1%). The predominant kinetic pattern was rapid increase (14 of 14, 100%) in the initial phase and washout (11 of 14, 78.7%) in the delayed phase. Associated non-mass like enhancement was shown in 4 patients, representing ductal carcinoma in situ. MR imaging helped detect additional sites of cancer other than the index lesion in 3 patients (21.4%). Enlarged axillary lymphadenopathy was identified in 7 of the 14 patients (50%). CONCLUSION Invasive micropapillary carcinoma appears as a mass with an irregular shape, irregular or spiculated margin and heterogeneous enhancement on MR imaging. Though these findings are not specific and are also observed with other breast malignancies, invasive micropapillary carcinoma frequently showed multiple lesions, accompanying non-mass enhancement and axillary lymph node enlargement.