This study demonstrates how clonal hematopoiesis (CH)–derived mutations could lead to erroneous reporting and treatment recommendations when tumor-only sequencing is employed. If data about the blood are not part of test results, mutations present in the blood may be misread as mutations in the tumor, which can potentially affect the therapies patients receive. Data presented at the annual meeting of the American Society of Clinical Oncology by Ahmet Zehir, PhD, Director of Clinical Bioinformatics at Memorial Sloan Kettering Cancer Center (MSK) was simultaneously published in <i>JAMA Oncology</i> on June 5.