MUC1 and idiopathic pulmonary fibrosis: A number of biomarkers have been explored to help in the differential diagnosis of common ILDs,[47–51] among them, KL-6 is a most promising.[8,19,31,32,52–55] KL-6 has also been reported to be associated with the progression of IPF and have been used for evaluating the efficacy of drugs targeting IPF, although its role is disputed.[19,22,47,56–62]