Immunohistochemical expression of P53 and cyclin D1 proteins in follicular thyroid tumors: evaluation of their significance

The sequential mutational events which may underlie the tumorigenesis of thyroid neoplasia are gradually becoming apparent. To clarify the role of P53 and cyclin D1 in the oncogenesis and tumor progression of thyroid neoplasms, we examined the immunoreactivity of these proteins in one hundred and thirty [130] thyroid tumors originating from the follicular epithelium using immunohistochemistry. The tumors were divided into two groups group I: included thirty five [35] follicular adenomas and group II: included ninety five [95] follicular carcinomas; 65 of which were well differentiated [WDC] while the remaining [30] were poorly differentiated [PDC]. P53 positivity was more frequent in group II [20/95; 21.1%] than in group I [6/35; 17.1%] and in PDC [11/30; 26.6%] than WDC [9/65; 13.8%]. On the other hand, cyclin D1 positivity was frequent in WDC [21/65; 32.3%] and rarely seen in adenoma group [2/35; 5.7%]. Co -positivity for P53 and cyclin D1 proteins was more observed in PDC [5/30; 16.7%] than in WDC [3/65; 4.6%]. The study suggested that cyclin DI may be involved in the thyroid oncogenesis and concluded that both proteins may be incriminated in the progression of follicular thyroid neoplasms. Moreover, we found that age at the time of diagnosis, the histologic differentiation, necrosis in primary tumor, extrathyroidal invasion and the presence of distant metastases are important prognostic and risk factors. In addition, our study revealed that the detection of P53, but not cyclin D1, in primary follicular carcinomas is a significant independent prognostic indicator which, together with the above mentioned important prognostic factors, may be of value in the theraputic planning of these tumors