Low-estrogen receptor-positive breast cancer: The impact of tissue sampling, choiceof antibody, and molecular subtyping

摘要

To the Editor: Iwamoto et al1 have analyzed the clinically important subgroup of estrogen receptor (ER) -positive breast cancers in which only 1% to 9% of neoplastic cells expressed ER by immunohis-tochemistry. The microarray gene-expression profiles of low-ER-expressing (1% to 9%) early breast cancers were elegantly investigated. The authors concluded that approximately 25% of the 1% to 9% ER immunohistochemistry-positive breast cancers are potentially endocrine-sensitive cancers, and a second RNA-based ER assessment may help identify these ESR1 mRNA-positive immunohistochemistry-borderline breast cancers. Although we agree with the main conclusions of this study, some issues need to be considered.