Predictive molecular diagnostics in breast cancer What are the requirements for pathology today and in the future?

With an increasing number of targeted therapy options for the treatment of solid tumors, the demands on predictive molecular diagnostics for pathology are growing. In breast cancer the need to determine genomic predictive markers for available targeted therapies has so far been manageable (detection of PIK3CA mutations in endocrine pretreated luminal tumors and the search for NTRK fusions indicated only in secretory breast cancer). At the latest in cases of nonresponse to first-line or second-line standard treatment, more comprehensive diagnostics using next generation sequencing (NGS) panel diagnostics makes sense. This should be suitable for clarifying resistance mechanisms, e.g. against endocrine therapy or cyclin-dependent kinase 4/cyclin-dependent kinase 6 (CDK4/6) inhibitors and to identify indications for therapies currently in development. The interpretation should be carried out in a quality assured manner in accordance with international standards and the interdisciplinary tumor board should make a transparent and standardized report available in a timely manner.