Objectives To evaluate the value of the vascular index (VI) on Superb Microvascular Imaging (SMI; Canon Medical Systems Corporation, Tokyo, Japan) in comparison with grayscale ultrasound (US) alone for assessing breast masses. Methods We evaluated a total of 70 breast masses (36 malignant and 34 benign lesions) in 70 consecutive patients using grayscale US and SMI. Two breast radiologists analyzed grayscale US alone and the combination of grayscale US and SMI. They also measured the VI based on SMI. The diagnostic performance of grayscale US alone and the combination of grayscale US and SMI was compared. The VI was compared between benign and malignant masses, and the optimal cutoff value was determined. In addition, the interobserver agreement in imaging analyses and the VI was assessed. Results The interobserver agreements in imaging analyses and the VI were almost perfect. The VI of malignant breast masses was significantly higher than that of benign lesions (P < .001). The optimal cutoff value of the VI for differentiating between malignant and benign breast masses was 2.95, with sensitivity of 86.1% and specificity of 91.2%. The diagnostic performance values of grayscale US alone and the combination of grayscale US and SMI were 0.824 and 0.912, respectively, for reader 1 (P = .028) and 0.795 and 0.853 for reader 2 (P = .101). Conclusions The VI on SMI was significantly higher for malignant breast masses than for benign lesions, with high interobserver agreement. Our study suggests that the combination of grayscale US and SMI with the VI could improve the characterization of breast masses.

Background Invasive micropapillary carcinoma (IMPC) is a rare subtype of breast cancer and is presumed to have a poorer survival outcome than invasive ductal carcinoma (IDC). However, studies for clinical outcomes including imaging features are still scarce. Purpose To investigate differences in clinical outcomes between IMPC and IDC and to determine prognostic factors indicating survival, including imaging features. Material and Methods This retrospective study was approved by the institutional review board. Between 2007 and 2012, 308 women diagnosed with IMPC were matched with patients from a group of 6816 women diagnosed with IDC. Patients were matched with 17 clinicopathologic covariates using propensity score matching. Recurrence-free survival (RFS) and overall survival (OS) were compared between the IMPC and IDC groups using Kaplan–Meier estimates. Log-rank tests were performed to compare the survival curves. A Cox proportional hazard model was used to analyze the association of imaging features with survival. Results In total, 308 matched patient pairs were available for survival analysis. The IMPC group showed worse total RFS (hazard ratio [HR] = 1.63, P = 0.016), local RFS (HR = 2.86, P = 0.042), and distant RFS (HR = 1.85 P = 0.018), but there was no significant difference in OS (HR = 1.30, P = 0.335). A mass with calcification on mammography was an independent factor for worse RFS in the IMPC group and combined IMPC and IDC groups. IMPC subtype was a significant independent factor for worse RFS in the combined groups. Conclusion The IMPC group showed poorer recurrence-free survival outcomes than the IDC group. A mass with calcification on mammography were associated with poor RFS.