Getting deep in the luminal B breast cancer subtype and its ki67 cut-off value

Inside the luminal breast cancer (BC) group, the B subclass carries a worse prognosis and is less responsive to hormonal treatment. Identification of the luminal B group, by Sorlie and colleagues [1], has been less consistent than other subclasses; and gene signatures based in estrogen-related genes or proliferation are better to identify this BC subclass. Cheang and colleagues genetically evaluated 144 luminal ER-positive HER2-negative tumors by IHC; they found a ki67 cutoff value of 13.25% to differentiate B from A subclasses [2]. No differentiation for PR status was done. The luminal B subgroup is usually defined as ki67 >13 if ER-positive, as well as HER2-positive or PR-negative. The target of this abstract is to evaluate behavior of different luminal B subsets.