Endocrine Abstracts

The loss of regulatory control of the cell, leading to unrestrained cell proliferation, is a hallmark of cancer. In a number of cancers, over expression of cyclin A and cyclin B1 proteins has been reported and in some instances the level of expression correlated well with the grades of malignancy. In the present study, we analyzed, by immunohistochemistry, the expression of cyclins A and B1, proteins enable passing G(2)-restriction point, in different histological variants of papillary thyroid carcinomas (PTC). We investigated immunostaining patterns in 40 tissue specimens of PTC for cyclin A and B1 which were divided in 3 groups: 20 classical PTC, 9 follicular variant of papillary thyroid carcinoma (FVPTC) and 11 other that FVPTC nonclassical PTC. Nuclear and/or cytological immunostaining detected in ≥5% of tumor cells was considered the cut-off for both cyclins. We observed a significant differences in expression of cyclin A and B1 between the groups. The highest expression was observed in group of other that FVPTC nonclassical PTC, the lowest expression was observed in group of classical PTC. The results of the study may potentially explain more aggressive character of other that follicular, nonclassical, variants of PTC. Evaluation of cyclins A and B1 in various thyroid lesions may be helpful in diagnostically doubtful cases. However, we cannot yet consider cyclins as a prognostic markers because the group of nonclassical PTC is to small.