CLDN10 and idiopathic pulmonary fibrosis: This concept of migratory club cells as pathogenic participants in IPF is compatible with our observations that Cldn10-positive club cells with morphological pleomorphism, supposedly immature or reverted club cells, are widely distributed in IPF lungs, i.e. in fibroblastic foci (Figure 1E & F; Figure 2G), areas with honeycomb change (Figure 2J & K), and fibrotic interstitium as well (Figure 2M; Figure 5F & I).