Abstract

Globally, Breast Cancer (BC) is the leading cause of cancer death among women. About 75% of patients are diagnosed with hormone-dependent tumors and are set to receive Endocrine Therapy (ET) targeting the estrogen receptor. Unfortunately, a significant proportion of these patients develops ET resistance. Still controversial, studies have proposed that Estrogen Receptor-Alpha Gene (ESR1) alterations may underlie ET resistance. Here, we describe the use of a Chromogenic in Situ Hybridization (CISH) assay for the assessment of ESR1 amplification in primary tumors and recurrences. This assay could be a useful clinical tool with therapeutic implications for estrogen receptor positive BC patients.