Lymph node involvement in immunohistochemistry-based molecular classifications of breast cancer.

Background: Prognosis and treatment options differ for each molecular subtype of breast cancer, but risk of regional lymph node (LN) metastasis for each subtype has not been well studied. Since LN status is the most important predictor for prognosis, the aim of this study is to investigate the propensity for LN metastasis in each of the five breast cancer molecular subtypes.

Methods: Under an institutional review board-approved protocol, we retrospectively reviewed the charts of all pathologically confirmed breast cancer cases from January 2004 to June 2012.