Diagnosis of a SMARCA4 ‐deficient undifferentiated tumor using multigene panel testing: A case report

KEY CLINICAL MESSAGE: SMARCA4‐deficient thoracic carcinoma is a malignant tumor that may present as cancer of unknown primary. This tumor is refractory and requires a novel approach. In addition to identifying therapeutic targets, multigene panel testing can reveal novel genetic mutations, leading to more pathologically relevant diagnoses and appropriate tumor care. ABSTRACT: SMARCA4‐deficient undifferentiated tumors are characterized by SMARCA4 inactivation. We present a case of a 74‐year‐old man with an undifferentiated tumor and a novel SMARCA4 mutation detected using multigene panel testing. The tumor was multiagent and refractory to three chemotherapy lines. The test results helped guide appropriate medical management.