Luminal B breast tumors are not HER2 positive – authors' response

Excerpt

The letter from Drs Bhargava and Dabbs [1] expressed concern with the immunohistochemical (IHC) criteria we used to define breast cancer molecular phenotypes in our study [2]. Although expression arrays are the 'gold standard' for defining these subtypes, there is sufficient evidence to suggest that the markers we selected provide a reasonable approximation of molecular phenotypes, as determined by gene expression profiling. For a large study such as ours, in which we collected more than 2,800 formalin-fixed, paraffin-embedded tissue samples from cancers occurring over a 20-year period, logistical and technical issues precluded the feasibility of our conducting expression array analyses. The obvious limitation of using IHC markers to define subtypes is that this may result in the misclassification of some tumors. …