We investigated the prognostic importance of pre-operative Breast Imaging Reporting and Data System classification in ultrasound imaging.

Histopathological differences and disease-free survival were analyzed in Breast Imaging Reporting and Data System classification subgroups. Univariate and multivariate analyses were used to identify the prognostic factors.

We identified 531 invasive breast cancer patients eligible for this study. Most patients classified as Breast Imaging Reporting and Data System 5 had large tumors and a higher rate of lymph node metastasis. However, hormonal receptor or HER-2 status did not differ according to Breast Imaging Reporting and Data System classification. During a median post-operative follow-up of 42.0 months, 43 patients were diagnosed with a disease-specific event. Disease-free survival was significantly lower in patients with Breast Imaging Reporting and Data System 5 than in patients with Breast Imaging Reporting and Data System 3–4. Subgroup analysis of patients with invasive breast cancer of Stage I showed that Breast Imaging Reporting and Data System 5 was an independent negative prognostic indicator of disease-free survival (hazard ratio 9.195; 95% confidence interval, 1.175–71.955; P = 0.035).

Breast Imaging Reporting and Data System classification might be considered as prognostic factors especially in Stage I breast cancer. Further confirmatory studies are needed.