Tenascin expression in idiopathic interstitial pneumonia

The expression of tenascin, an extracellular matrix glycoprotein, was studied immunohistochemically in the lungs of 22 autopsy cases, including chronic idiopathic interstitial pneumonia (chronic IIP) associated with lung cancer (5 cases), chronic IIP without lung cancer (6 cases), acute idiopathic interstitial pneumonia (acute IIP; 6 cases) and alveolar pneumonia (AP; 5 cases). In the honeycomb lesion of chronic IIP, tenascin expression was observed in the basement membrane of metaplastic epithelia and in the subepithelial stroma of thickened septa with fibrosis. In the non-honeycomb area of chronic IIP, tenascin was expressed in mildly thickened alveolar walls with fibrosis. The distribution of tenascin expression in chronic IIP associated with lung cancer resembled that in chronic IIP without lung cancer. In acute IIP, tenascin expression was observed in mildly thickened alveolar walls with fibrosis, in organizing hyaline membranes. In AP, tenascin was expressed in organizing exudate of alveoli and was scarcely observed in the alveolar wall. It is very possible that tenascin is associated with the fibrosing process and remodelling in IIP, and has a promoting effect in carcinogenesis in IIP lung.