Expression of epidermal and nerve growth factor receptors in human thymus and thymomas

The expression of epidermal growth factor (EGF) and nerve growth factor (NGF) receptors has been investigated by immunohistochemical analysis in eight normal human thymuses and in 15 thymomas. Thymomas were classified into five different histological types--medullary, mixed, predominantly cortical, cortical thymoma and well-differentiated thymic carcinoma. In fetal and paediatric normal thymus, EGF-receptor was expressed by subcapsular, cortical and medullary epithelial cells, whereas immunoreactivity for NGF-receptor was detected on only subcapsular and medullary epithelial cells. In thymomas, independent of their histological type, EGF-receptor was expressed by a large majority of epithelial cells. In contrast, the pattern of expression of NGF-receptor in thymomas was different for the various histological types. These findings indicate that the expression of both EGF and NGF receptors in human thymomas substantially reflects their expression in normal thymus, and suggest that EGF and NGF may play a role in the ontogenesis of the human thymus as well as in the histogenesis of thymomas.