[Pneumatosis intestinalis--histology, immunocytochemistry and new theory of morphogenesis].

Based on the light microscopical and immunocytochemical findings in two cases of pneumatosis intestinalis, a new theory is advanced on the morphogenesis of the cysts that can be observed in this disease. The cavities identifiable in both cases in the submucosa of the small intestine and of the colon, respectively, were partially lined by histiocytes and foreign-body giant cells. Most of the lumina found in the subserosa of the stomach, small intestine and colon had an identical aspect. In addition, there were numerous true cysts here with a narrow, single-layered cells seam, showing the immunocytochemical characteristics of the mesothelium, but not the capillary endothelia. Thus, contrary to previous assumptions, pneumatosis interstinalis apparently does not develop from cystic dilatation of gas-filled lymph vessels that shrink and disappear in the process of an inflammatory foreign body reaction. Rather, the disease initially seems to manifest itself through gas-filled pseudocysts partially bordered by histiocytes and foreign-body giant cells, which become secondarily mesothelialized in the subserosa. Lymph vessels would thus not have significance for the morphogenesis of this disease.