MUC1 and interstitial lung disease: After the resumption of durvalumab treatment, his respiratory symptoms (grade-3 dyspnea on the mMRC scale) and X-ray features of bilateral ground-glass opacities mixed with consolidation were aggravated (blue circle and blue arrows), and his serum KL-6 level markedly increased to 1,012 U/mL, reflecting a recurrence of severe TR-ILD.