EXPRESSION OF E-CADHERIN AND ALPHA-CATENINS AND BETA-CATENINS IN THYMOMA

Expression of the cell adhesion molecules including E-cadherin and its cytosolic binding proteins, alpha- and beta-catenins, has been widely studied in a variety of tumours, but not, to date, in thymic epitheli al tumours. To observe the expression pattern of these adhesion molecu les, immunohistochemical stains for E-cadherin (E-CD) and alpha- and b eta-catenins were performed on 89 cases of thymoma which were classifi ed as cortical (57 cases), mixed (18 cases), and medullary (14 cases), based on the classification of Marine and Muller-Hermelink. The major ity of cortical thymomas showed diffuse and homogenous membrane immuno reactivity for these molecules (88 per cent for E-CD; 86 per cent for alpha-catenin; 91 per cent for beta-catenin) and the remaining cases s howed heterogenous immunoreactivity, whereas almost all mixed and medu llary thymomas revealed decreased expression or were negative. In each histological subtype of thymoma, the expression did not correlate wit h invasion or with the presence of myasthenia gravis. These results in dicate that the expression of E-CD and alpha- and beta-catenins is mor e closely associated with the histological subtypes of thymoma than wi th their biological behaviour. (C) 1998 John Wiley & Sons, Ltd.