Expression of bcl-2 , p53 Protein and Aggressiveness in Thymic Epithelial Tumor

Cho, Sung Rae; Jeon, Do Hwan

Abstract

BACKGROUND: The distinction between non-invasive and invasive or thymic carcinoma has been severely compromised by lack of objective morphological criteria. A reliable biological marker of tumor aggressiveness is, therefore, mandatory for predicting tumor behavior. MATERIAL AND METHOD: Thirty thymic epithelial tumors, including 7 non-invasive thymoma, 10 invasive thymoma, and 13 thymic carcinoma of the Rosai's classification; and 5 stage I, 7 stage II, 2 stage III, and 3 stage IVa of the Masaoka stage of thymoma were investigated for expression of bcl-2 and p53 proteins by immunohistochemistry. RESULT: The thymic epithelial cells showed positive immunostain for bcl-2 in 0 (0%), 3 (30%), 8 (61.5%) of categories in the Rosai's classification respectively and in 0 (0%), 1 (14.3%), 2 (100%), 0 (0%) of stage I, II, III, IVa of the Masaoka stage respectively. Thymic carcinoma, and high stage thymoma had significantly higher proportion of bcl-2 expression than thymoma (p=0.021) and low stage thymoma (p=0.011). However, p53 showed no correlation with the histological subtypes nor with clinical aggressiveness. Bcl-2 expression appeared to be positively correlated with p53 immunoactivity (p=0.007, kappa=0.525).
CONCLUSION
These date indicate that bcl-2 expression correlates with aggressiveness in thymic epithelial tumors, but further studies on mutation of p53 protein is necessary because bcl-2 expression appeared to be positively correlated with p53 immunoactivity.