Molecular testing in breast cancer

Abstract

Molecular testing in breast cancer has been used for many years to guide treatment selection and provide prognostic information, as has been exemplified by the immunohistochemical (IHC) assessment of molecular markers such as ER, PgR, and/or HER2. Additional information can be derived by the assessment of proliferation status achieved through IHC evaluation of Ki67. During the last years, newly emerged technologies have expanded the palette of molecular tests becoming available in breast cancer, namely, gene expression profiling leading to the generation of prognostic gene signatures and gene signatures of specific pathway activation status, circulating tumor cells detection and enumeration methods, and sequencing techniques currently used for the assessment of BRCA1/2 mutational status, with next-generation sequencing methods setting the promise to elucidate the molecular landscape of this common disease. In the present chapter, we provide a comprehensive overview of all molecular tests currently used in breast cancer, giving additional information about newly emerging molecular tests that promise to improve the clinical management of our patients.