Assessment of molecular markers in small biopsy specimens of breast carcinoma

Abstract

This talk focuses on hormone receptor (HR) and HER2 assessment of fine needle and core biopsy samples in diagnostic practice. Assessment of small biopsies is required for primary carcinomas when neoadjuvant therapy is planned and for metastatic tumours when the primary is not available. A number of technical and biological factors (e.g., tumour heterogeneity) are important. There is evidence that HR testing by immunohistochemistry (IHC) in core biopsy is at least equivalent to testing of excisional specimens. HR testing of cell block material also shows good concordance with excisional results. HER2 assessment is affected by national variations such as pharmaceutical funding guidelines and adoption of bright-field in situ hybridisation (ISH). Relatively high rates of discordance are seen in small biopsy samples tested by HER2 IHC. ISH techniques show better correlation of results between small biopsy and surgical specimens. Assessment of molecular markers in small biopsy samples is likely to be affected by a number of changes in laboratory and clinical practice in the medium term future.