Objective: The aim of the study was to investigate the morphological and the molecular-biological changes of the lung progenitor cells and their niches in idiopathic interstitial pneumonias (IPF) and lung sarcoidosis (LS). Method: We performed an immunohistochemical study on open lung biopsies from 250 patients (usual IPF -87, desqvamative interstitial pneumonia-37, nonspecific IPF -42, Cryptogenic IPF -20, LS -32, control -34 patients). Immunochemistry was done on step paraffin sections with monoclonal and polyclonal antibodies: Apo-Cas, PCNA, 18, 19, PDGF, FGF, IGF II, CD 34, MMP 1, 2, 7, 9, TIMP 4, CD 68, SMA, EMA. Results: Deep injury of Clara cells together with pneumocytes II and their nishes were found in usual IPF, SK with prominent IPF and desqvamative interstitial pneumonia. Myofibroblast proliferation, neoangiogenesis, adenomatosis and fibrosis with high production of TNFα, TGF-β, PDGF, FGF, IGF II, CD 34, MMP 1, 2, 7, 9, TIMP 4 accompanied proliferation of these epithelial cells. While in other variants of IPF pathological changes were localized in the interstitium, vessels and basal bronchiolar epithelial cells. Conclusion: Localization of injury and inflammation in progenitor cells niches results in pathologic reparation, sclerosis and precancer lesions.