Thoracic SMARCA4‐deficient undifferentiated tumour (SMARCA4‐UT) is a high‐grade malignant neoplasm caused by the loss of function of SMARCA4, a key member of the SWItch/Sucrose‐NonFermentable (SWI/SNF) adenosine triphosphatase (ATPase)‐dependent chromatin remodelling complex.1 Here, SMARCA4 is linked to neoplasm.