Although SMARCA4-deficient NSCLC (frequently adenocarcinomas) may display histologic features of de-differentiation including loss of TTF1 expression and a solid growth pattern; thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UT) show undifferentiated round cell or rhabdoid features and reduced expression of epithelial markers such as cytokeratins and claudin-4. Here, CLDN4 is linked to non-small cell lung carcinoma.