IFNL1 and synovial sarcoma: The important role of IL‐29 in tumours and its potential use for clinical therapy has been widely discussed.8 Due to antiviral and immunoregulatory characteristics of IL‐29, studies also showed that IL‐29 performed significantly in the pathogenesis of inflammatory autoimmune diseases,9 for instance, systemic lupus erythematosus (SLE),10 rheumatoid arthritis (RA),11 psoriasis12 and Sjögren's syndrome (SS).13 The discovery of type III IFNs opens up a new field of IFN research in which IL‐29 is considered to be a core member.