IL34 and lung carcinoma: For IL‐34 staining, a monoclonal antibody 1D12 was used because the clone specifically detected IL‐34 in lung cancer cells17 and keratinocytes of the skins (Figure 1a, left), the latter of which are known to highly express IL‐34.5, 6 The lymph nodes showing reactive hyperplasia were negative for IL‐34 expression (Figure 1a, right).