Objective  To detect the expression of acetaldehyde dehydrogenase 2 (ALDH2) in invasive micropapillary carcinoma (IMPC) and explore the significance of ALDH2 expression levels in guiding neoadjuvant chemotherapy regimen for patients with IMPC of breast.

  Methods  Clinicopathological data of 298 patients with breast cancer who underwent neoadjuvant chemotherapy (NAC) at Tianjin Medical University Tumor Hospital from January 2009 to May 2014 were assessed. Of the 298 patients, 84 with IMPC and 214 with invasive ductal carcinoma of no special type (IDC-NOS). Eighty-four patients with IMPC and IDC-NOS were successfully matched by the propensity score matching method. Difference in the expression of ALDH2 between the IMPC and IDC-NOS groups was detected, and clinicopathological features, NAC response grade, and prognosis of patients with IMPC in different ALDH2 expression groups were analyzed.

  Results  The expression level of ALDH2 in IMPC was 48.8% (41/84), which was significantly higher than that in IDC-NOS (33.3%, 28/84), and the difference was statistically significant (P=0.041). In the IMPC group, the expression level of ALDH2 was positively correlated with N stage (r_s=0.348, P=0.017) and p53 mutation level (r_s=0.262, P=0.016) and negatively correlated with the grade of NAC response and disease-free survival (DFS) (all P<0.05).

  Conclusions  ALDH2 was highly expressed in IMPC and was negatively correlated with NAC response grade and DFS. IMPC patients with high ALDH2 expression should be surgically treated as soon as possible to prolong survival.