Tenascin and type IV collagen expression in liver cell dysplasia and in hepatocellular carcinoma

The extracellular matrix (ECM) located in and around tumors is different from normal organ stroma, and there is evidence that it is critically involved in carcinogenesis and malignant growth. Whereas an abnormal composition of ECM in hepatocellular carcinomas (HCC's) has previously been demonstrated, not much is known so far with respect to putative HCC precursor lesions. We have, therefore, systematically analyzed the immunohistochemical reactivity for two major ECM components, tenascin and type IV collagen, in three types of liver cell dysplasia (LCD), and compared the findings with patterns observed in HCC's of different types and grades. Tenascin reactivity was generally stronger in HCC's than in cirrhosis. In cirrhotic nodules harboring areas of LCD, tenascin expression was significantly lower in small cell LCD than in large cell LCD. Type IV collagen reactivity in and around HCC's decreased as a function of a lower differentiation grade. In both groups of cirrhosis, i.e. with or without HCC, cirrhotic nodules occupied by the small cell variant of LCD exhibited a significantly lower type IV collagen reactivity than those with large cell LCD or simple regenerative cells. Taken together these findings suggest that, similar to adenomatous hyperplasia, small cell LCD is characterized by an abnormal tenascin and type IV collagen expression, thus reflecting the defective ECM pattern observed in HCC's.