Expression of cyclins D1, D3 and p27 in thymic epithelial tumors

In this study, the expression of cyclins D1 and D3, as well as cyclin-dependent kinase inhibitor p27 in thymic epithelial tumors (thymomas) is examined. Histological specimens from 24 patients (11 males and 13 females) were submitted to classification according to WHO criteria. Staining for cyclins D1, D3 and p27 was applied and evaluation was performed for expression of D1, D3 and p27. Eighteen patients presented low-grade thymomas (nine B1, predominantly cortical; three B2, cortical; six B3, well-differentiated thymic carcinoma) and six patients benign thymomas (four A-medullary, two AB-mixed). The p27 expression in patients with benign thymomas was 42+/-26%, whereas in patients with low-grade thymoma, it was 11+/-13%. The expression of cyclins D1 and D3 was 2.8+/-2.7 and 10+/-6% for benign as well as 8.3+/-9.6 and 12+/-10% for low-grade thymomas, respectively. A statistically significant difference was revealed regarding the p27 expression through different grades (analysis of variance P-value 0.00076) and histopathological types of thymomas (P=0.0047). This finding of greater p27 expression in benign thymomas with progressive reduction in higher grades is compatible with observations on other soft tissue and solid tumors suggesting that p27 level decreases during tumor development and progression.