According to Rekhtman et al., the epithelial adhesion molecule Claudin-4 is expressed in SWI/SNF-deficient NSCLC, while almost no expression is observed in SWI/SNF-deficient undifferentiated tumors.10) Thus, Claudin-4 may serve as a criterion for determining the origin of tumors.9) This evidence concerns the gene CLDN4 and non-small cell lung carcinoma.