Invasive micropapillary carcinoma of the breast is of growing clinical significance. The purpose of this study was to identify the radiological imaging features for this type of breast carcinoma and the axillary lymph nodes. The study population consisted of 30 breast cancer patients (8 invasive micropapillary carcinomas and 22 other types of invasive ductal carcinoma). The breast lesions were evaluated with mammography, ultrasonography, and contrast-enhanced magnetic resonance imaging (MRI) prior to neoadjuvant chemotherapy. The pathological outcome of the axillary lymph nodes in 27 patients was correlated with the sonographic findings. Only contrast-enhanced MRI showed characteristic findings for invasive micropapillary carcinoma. Although invasive micropapillary carcinoma is commonly irregular in shape (7/8) compared with other types of invasive carcinoma (6/22) (p=0.012, χ2 test), a careful interpretation of radiological imaging to identify lesion borders helped the complete clearance of cancer cells from 6/8 patients with invasive micropapillary carcinoma in one-time breast conservative surgery. The positive and negative predictive values of sonography in diagnosing axillary lymph node metastases in cases of invasive micropapillary carcinoma were 100 and 50%, respectively. In conclusion, contrast-enhanced MRI reveals the irregular shape of invasive micropapillary carcinoma and helps conservative breast surgery to be performed safely. The pathological analysis of axillary nodes in cases of invasive micropapillary carcinoma may prove to be indispensable due to the relatively low negative predictive value of sonography.

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