['To explore the clinical characteristics and prognostic value of malignant calcification in operable breast cancer.', 'A total of 721 patients with invasive ductal carcinoma were divided into two groups based on whether malignant calcifications were observed on mammograms. The association of calcification with pathological features and survival were evaluated. The relative importance of each of the potential prognostic variables was tested using a Cox regression analysis.', 'Compared with tumors without calcification, those with calcification had a larger tumor size, more lymph node involvement, lower estrogen and progesterone receptor expression and higher human epithelial growth factor receptor 2 expression. The 8-year relapse-free survival was lower for patients with calcifications than for those without (77.5 vs 89.2%, P < 0.01). The 8-year overall survival for patients with calcifications was 82.2% compared with 91.9% for those without (P < 0.01). In multivariate analysis, node status, existence of calcification and tumor size were demonstrated to have a prognostic value for relapse-free survival. The node status, existence of calcifications and estrogen receptor status were also prognostic factors for overall survival.'] Is malignant calcification an important unfavorable prognostic factor in primary invasive breast cancer?