Bloom, Kenneth J.

Abstract Context. —Intratumoral heterogeneity of HER2 gene amplification has been well documented and represents subclonal diversity within the tumor. The reported incidence of intratumor HER2 amplification genetic heterogeneity ranges in the literature from approximately 5% to 30%. The presence of HER2 genetic heterogeneity may increase subjectivity in HER2 interpretation by the pathologist. Objectives. —To define HER2 genetic heterogeneity and to provide practice guidelines for examining and reporting breast tumors with genetic heterogeneity for improvement of HER2 testing in breast cancer. Design. —We convened an expert panel to discuss HER2 gene amplification testing by fluorescence in situ hybridization. Components addressed included a definition of HER2 amplification heterogeneity, practice guidelines for examination of the tissue, and reporting criteria for this analysis. Results. —Genetic heterogeneity for amplification of HER2 gene status in invasive breast cancer is defined and guidelines established for assessing and reporting HER2 results in these cases. These guidelines are additive to and expand those published in 2007 by the American Society of Clinical Oncology and the College of American Pathologists. Conclusion. —Standardized methods for analysis will improve the accuracy and consistency of interpretation of HER2 gene amplification status in breast cancer.

Biospecimens acquired during routine medical practice are the primary sources of molecular information about patients and their diseases that underlies precision medicine and translational research. In cancer care, molecular analysis of biospecimens is especially common because it often determines treatment choices and may be used to monitor therapy in real time. However, patient specimens are collected, handled, and processed according to routine clinical procedures during which they are subjected to factors that may alter their molecular quality and composition. Such artefactual alteration may skew data from molecular analyses, render analysis data uninterpretable, or even preclude analysis altogether if the integrity of a specimen is severely compromised. As a result, patient care and safety may be affected, and medical research dependent on patient samples may be compromised. Despite these issues, there is currently no requirement to control or record preanalytical variables in clinical practice with the single exception of breast cancer tissue handled according to the guideline jointly developed by the American Society of Clinical Oncology and College of American Pathologists (CAP) and enforced through the CAP Laboratory Accreditation Program. Recognizing the importance of molecular data derived from patient specimens, the CAP Personalized Healthcare Committee established the Preanalytics for Precision Medicine Project Team to develop a basic set of evidence-based recommendations for key preanalytics for tissue and blood specimens. If used for biospecimens from patients, these preanalytical recommendations would ensure the fitness of those specimens for molecular analysis and help to assure the quality and reliability of the analysis data.