CLDN4 and undifferentiated carcinoma: In addition, studies have suggested that staining for the epithelial tight junction protein claudin-4 may be useful, as SWI/SNF deficient soft tissue neoplasms in general lacked claudin-4 expression, whereas more than 80% of SWI/SNF deficient undifferentiated carcinomas exhibited expression of this protein [21, 22].