The Immunoexpression of Ki-67, Bcl-2, p53, and Tyrosine Kinase Receptors in Thymic Epithelial Tumors; Their Correlation with the WHO Histologic Subtypes and the Prognostic Value

Kim, Mi Jin

Abstract

BACKGROUND: The clinicopathologic features of thymic epithelial tumors are inadequate as predictors of the progression of these tumors because of their heterogeneous histology and varied biological behavior. We attempted to detect the expression of tyrosine kinase receptors and oncogenic markers to determine the correlation between these markers and the WHO classification of the tumors. METHODS: Forty-three surgically resected thymic epithelial tumors (37 thymomas and 6 thymic carcinomas) were immunohistochemically assessed on tissue arrays for c-KIT, her-2/neu, epidermal growth factor receptor (EGFR), p53. bcl-2 and Ki-67. RESULTS: The Ki-67 labeling index was significantly increased in thymic carcinoma (p<0.05). The overexpression of p53 protein was observed exclusively in type B3 thymoma (67%) and thymic carcinoma (83%). Bcl-2 was expressed in type A and AB thymomas as well as in thymic carcinoma. C-KIT was only present in thymic carcinoma (p<0.05), whereas the EGFR expression was significantly high in all types of thymomas, except for thymic carcinomas. Her-2/neu was not identified in any type of thymoma. CONCLUSION: This study suggests that the Ki-67 LI, bcl-2, p53, c-KIT, and EGFR protein expression may be useful markers for the subclassification of thymic epithelial tumors according to WHO schema and WHO classification correlated with the tumor staging. The overexpression of c-KIT in thymic carcinoma reveals that these patients would likely benefit from an anti-c-KIT treatment.