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Pathomorphological examination of large bronchi in patients with occupational diseases, lung cancer, and in subjects exposed to radiation revealed structural and functional heterogeneity of the epithelium: the presence of focal atrophy, metaplasia, hyper- and dysplasia in the same biopsy specimen. This phenomenon was termed as instability of the epithelium. Thickness of the epithelium greatly varied, especially, in neoplastic processes. Atrophy and epithelial instability phenomenon are interpreted as morphological markers of ecological and oncological risk.

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Diffuse progressive atrophy of the bronchial epithelium and mucosa are the main changes detected in the biopsy specimens of large bronchi in lung cancer. Unstability of the bronchial epithelium in lung tumors (alternating atrophy, metaplasia, hyperplasia, and dysplasia) is described. Key Words: lung cancer; bronchial epithelium; bronchial biopsy; atrophy; instability phenomenonPathomorphosis of respiratory diseases [7,8] and many new lung diseases induced by ecological factors [3,4,6,11] are responsible for modification of pretumor processes. Reduced capacity to DNA repair and induced and spontaneous mutations facilitate malignant transformation of target cells [1]. Normal cell can be transformed into tumor cell not only due to gene mutations, but also due to epigenomic, or regulatory disorders [1,10]. Initial sign of central lung cancer is desquamation of bronchial epithelium (BE), one of the most important markers of its atrophy, denudation of the basal layer, and damage to basal cells, followed by their hyperplasia and metaplasia. Unstable tissue proliferation is believed to play an important role in this process [2]. Atrophic processes, highly prevalent in recent years, attracted our attention, because of the priority importance of early diagnosis of cancer.Our purpose was a pathomorphological and endoscopic study of the large bronchi in lung cancer for evaluating the role of structural changes in the airways in the morphogenesis of cancer of the respiratory organs. MATERIALS AND METHODSClinical, endoscopic, and pathomorphological studies were carried out in 250 patients with central and peripheral cancer. Among histological forms of lung cancer, squamous-cell (52%) and small-cell (30%) cancer and adenocarcinoma (15%) predominated, in the rest cases mixed forms were identified. Specimens of large bronchi were examined under light optic and electron microscopes and analyzed by autoradiography. For light microscopy the fragments were fixed in 10% neutral formalin and treated routinely. Paraffin sections were stained with hematoxylin and eosin with Pearl's reaction, elastic fibers were stained by the method of Van-Gieson followed by Weigert's resorcin-fucsin poststaining, and periodic acid Schiff reaction was performed.For electron-microscopy, small fragments (no more than 1 mm 3) were fixed in 4% paraformaldehyde and 1% OsO 4. After standard treatment for electron microscopy, the tissue was embedded in epon-araldite. Scmithin sections were stained with 1% azur II and Schiff reagent. Ultrathin sections after double-contrasting were examined under a JEM 1010 electron microscope at accelerating voltage of 80 kV.