[Comparison of prognosis between invasive micropapillary carcinoma and invasive ductal carcinoma of breast: a single center, retrospective case-control study].

Objective: To elucidate the clinicopathological characters and prognostic factors of invasive micropapillary carcinoma of the breast (IMPC) by compared with invasive ductal carcinoma, not otherwise specified of the breast (IDC). Methods: The retrospective study was performed with female patients who had undergone curative resection for breast cancer without neoadjuvant chemotherapy from June 2008 to April 2016 in Breast Center of Beijing Hospital. Forty-seven mixed or pure IMPC patients and 93 pure IDC patients(admitted in the same center from October 2008 to January 2016 ) were matched for tumor stage, nodal status and age. Follow-up was done every 3 to 6 months postoperatively. The deadline was July 31, 2016. The curves of disease free survival and overall survival were drawn by the Kaplan-Meier method, and survival rates were compared by means of the Log-rank test. Potential prognostic variables that were identified on univariate analysis were analyzed with Cox's proportional hazards regression model for multivariate analysis. The χ(2) test or Fisher's exact test was used to compare distributions across 2 groups and the Mann-Whitney U test or t test was used to analyze the medians or means of 2 groups. Results: With exact matches, the rates of lymphovascular invasion (LVI) (29.8% vs . 12.9%, χ(2)=5.885, P =0.015)and histological grade 3 (40.4% vs . 21.5%, χ(2)=-2.690, P =0.007) were both significantly higher in patients with IMPC than that in IDC group, but the survival between the two pathological types were not significantly different (all P >0.05). The percent of IMPC component didn't influence the clinicopathologic characters (all P >0.05), but a significantly longer median disease free survival (χ(2)=11.731, P =0.001) when the patients had more than 50% of IMPC component was found. Conclusions: Higher rates of LVI and histological grade 3 were found in IMPC than that in IDC, but the survival was comparable between the two groups. A longer DFS occurred in patients with IMPC component more than 50%.