We review the current knowledge on alterations of the major basement membrane (BM) components and their cellular integrin receptors in benign and malignant tumors of epithelial and mesenchymal origin. While benign tumors usually exhibit a continous BM, recent analyses provide evidence that invasive growth of carcinomas coincides with (a) a loss in a proper BM, (b) changes in the type of integrin receptor expression and (c) the retained ability of certain tumor cells to synthesize matrix components. This latter aspect has been regarded as a potentially beneficial 'host' mechanism against invasive growth. This assumption is strongly supported by the finding of a positive correlation between the extent of BM loss and both a lesser degree of tumor differentiation and a worse prognosis of tumor growth. The resulting concept indicates that in carcinomas an imbalance in the cell-matrix interaction is the leading element in invasive growth. In mesenchymal tumors a somewhat different role of the BM can be observed. Thus, the qualitative and quantitative expression of major BM components in benign mesenchymal tumors closely relates to the BM pattern of normal tissues providing a histogenetically oriented classification of benign mesenchymal tumors. Most well-differentiated sarcomas retain a BM pattern close to that of the histogenetically related tissue, although in poorly differentiated sarcomas no such attribution to a histogenetic orientation of the tumor cells can be found.

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