MUC4 and idiopathic pulmonary fibrosis: In addition, although the expression level of Mucin 4, cell surface associated (MUC4) has been reported to be increased in IPF[49], we observed no association between MUC4 and EGFR-TKI-induced ILD (P = 1.74 × 10−1–9.99 × 10−1).