Editorial: 2021 European Society for Medical Oncology (ESMO) Recommendations on Laboratory Diagnostics for RET Gene Fusions and Mutations: A New Era in Targeted Therapy for RET-Altered Solid Tumors.

During the past four decades, the identification of phenotypic changes in malignant tumor cells has been refined by the standardization of immunohistochemistry methods. Regulatory-approved companion diagnostics were initially developed for immunohistochemistry and to support early tumor tissue-based clinical trials. In the last decade, molecular profiling and gene sequencing data have identified specific molecular targets that have resulted in increasing drug development programs and regulatory approvals. As an example, RET-altered cancers include RET gene mutations and RET gene fusions. In January 2021, the European Society for Medical Oncology (ESMO) published new guidelines for routine clinical laboratory detection of targetable RET gene rearrangements and mutations. FDA approval has now been given for selpercatinib for RET fusion-positive NSCLC and papillary thyroid cancer, and RET mutation-positive thyroid cancer. This Editorial aims to present a brief overview of the evolution of personalized medicine in oncology and how the 2021 ESMO guidelines have anticipated the need to detect targetable RET-altered tumors using technology currently available in accredited clinical diagnostic laboratories.