Interestingly, FN1+SPP1+ monocyte-derived macrophages are believed to be involved in the pathogenesis of canine idiopathic pulmonary fibrosis (5, 33) and profibrotic SPP1+ monocyte-derived macrophages were also reported in human COVID-19, pulmonary fibrosis and lung cancer (4). The gene discussed is SPP1; the disease is lung cancer.