DIFFERENT EXPRESSION OF ADHESION MOLECULES ON STROMAL CELLS AND ENDOTHELIAL-CELLS OF CAPILLARY HEMANGIOBLASTOMA

Cell-cell and cell-matrix interactions are essential for many basic fu nctions, including differentiation and development. In pathological co nditions such as inflammation and tumorigenesis adhesive events also p lay a major role. Cellular adhesion is mediated by specific molecules expressed by both normal and neoplastic tissues. Capillary hemangiobla stoma is a tumor of controversial origin, characterized by two major c omponents, vacuolated stromal cells and a capillary network. In order to shed light on the differentiation of the stromal cells and the inte ractions between the two major components of hemangioblastoma we studi ed the expression of several adhesion molecules by immunocytochemistry . The endothelium-associated adhesion molecules (ICAM-1, ICAM-2, VCAM- 1, PECAM-1 and ELAM-1) were expressed by endothelial cells within the tumors, but not by stromal cells. In contrast, the stromal cells showe d strong neuronal cell adhesion molecule (NCAM/CD56) expression, furth er distinguishing them from endothelial cells. In addition, the stroma l cells expressed CD44, which is of interest, as this membrane protein is linked to ezrin, a cytoskeleton-associated protein also expressed by stromal cells. We conclude that the stromal cells and endothelial c ells of capillary hemangioblastoma exhibit quite divergent expression patterns of adhesion molecules. The NCAM expression in stromal cells s uggests neuroectodermal or mesenchymal differentiation of this tumor. In addition, the NCAM expression could contribute to the sometimes pro blematic differential diagnosis between capillary hemangioblastoma and metastatic renal cell carcinoma of the central nervous system.