DISTRIBUTION OF THE VLA FAMILY OF INTEGRINS IN NORMAL SALIVARY-GLAND AND IN PLEOMORPHIC ADENOMA

The extracellular matrix (ECM) and the alterations in tumour stroma affect the biologic behaviour of tumours. These interactions are, at least in part, mediated by the integrin superfamily. In this study we examined the immunohistochemical expression of the ''very late activation'' (VLA)-integrins in pleomorphic adenomas and in the corresponding normal tissues. Normal salivary gland expresses integrins in the myoepithelial cells (MEC) and in the basal and dark cells of ducts. This pattern is retained in pleomorphic adenoma. Regardless of the staining intensity, these tumour cells have a VLA expression similar to normal basal and dark cells, with only a few cells bearing MEC characteristics. We suggest that the tumour cells of pleomorphic adenoma have a common origin but show different stages of differentiation. Only cells bearing basement membrane (BM)-associated material form typical tubulo-ductal structures.