Estudo imuno-histoquímico da fosfo-histona-3 (serina-10) em neoplasias de tireóide

Abstract

Thyroid cancer is the most common endocrine malignancy and accounts for almost 2% of all cancers. Its incidence has been increasing over the last decades worldwide, especially because of the papillary thyroid carcinoma (PTC). Even though the mortality of PTC is low, a few cases show an aggressive behavior leading rapidly to death. Among 10 and 15 % of fine needle aspiration cytologies fail in distinguishing between benign thyroid lesions from malignant ones. In some cases, even the diagnosis from a biopsy can be difficult. In the last years, countless studies have emerged to show evidences of epigenetic changing contributions, such as post translational modification of histones, in the development and progression of various cancer types. Based on these assumptions, the present study aimed at assessing the role of the histone H3 phospho S10 (H3S10p) in thyroid neoplasm, in order to determine its contribution in establishing a precise diagnosis and also a behavioral prediction. For this, an immunohistochemistry tool was needed to investigate H3S10p expression in 14 samples of normal thyroid tissue, 10 cases of follicular adenomas and 61 cases of thyroid carcinomas (papillary, follicular, oncocytic and medullary) including 48 samples of PTC, emphasizing in the comparison of histopathological findings in PTC cases. Each reaction was analyzed qualitatively and quantitatively by using Quickscore index. The current study showed a gradual decrease in H3S10p reactivity from normal thyroid to adenomas, and from these to carcinomas, thus showing a low or absent reactivity in malignant cases. However, the use of this association as an auxiliary tool in thyroid cancer diagnosis cannot be taken as an absolute rule, since we also found negative reactivity in normal thyroid and adenomas. There was no significant difference in Quickscore findings among all histological types of carcinomas. There was also no significant association between H3S10p reaction and clinical and histopathological parameteres, except for age. These results just point out to the involvement of the H3S10 in thyroid carcinogenesis. In addition, it becomes evident that the histone modification assessment in understanding of tumor carcinogenesis is surely interesting.