Clinical Significance of P53 Protein Expression in Papillary Thyroid Carcinoma

BACKGROUND: Although mutations in the p53 suppressor gene in thyroid carcinoma have usually been detected in anaplastic carcinoma, P53 protein expression has been detected immunohistochemically in papillary thyroid carcinoma (PTC). In the present study, we examined the immunohistochemical expression of P53 protein in PTC to investigate the relations between its expression and the clinicopathologic features. METHODS: The study was performed on 68 patients in whom thyroidectomy with lymph node dissection had been performed to treat PTC at Teikyo University Hospital. Expression of P53 protein was evaluated immunohistochemically in sections of paraffin-embedded tissue in 68 primary tumors and 196 lymph node metastases. RESULTS: Overexpression of P53 protein in the primary tumor was observed in 29 cases (43%). Statistical analysis revealed significant correlation between P53 protein expression in the primary tumor and large tumor size (unpaired t-test: p < 0.01), the presence of lymph node metastasis (unpaired t-test: p < 0.05), and the mean number of lymph node metastases (unpaired t-test: p < 0.05). Although 29 (43%) of the primary tumors overexpressed P53 protein, 143 (73%) of the metastatic lymph nodes overexpressed P53 protein irrespective of whether there was P53 overexpression by the primary tumor. CONCLUSIONS: The results of this study suggest that immunohistochemistry for P53 in the primary tumor could be useful in the clinical evaluation of patients with PTC. Moreover, P53 protein overexpression in lymph node metastasis may be useful as a treatment guide or target for lymph node recurrences.