IMMUNOHISTOCHEMICAL ANALYSIS OF EXPRESSION OF BCL-2 PROTEIN IN PAPILLARY CARCINOMAS AND PAPILLARY MICROCARCINOMAS OF THE THYROID GLAND
Aim: To compare the expression of anti–apoptotic protein bcl-2 and tissue proliferation Ki-67 antigen in tissues of human papillary thyroid carcinoma (PTC) and papillary thyroid microcarcinoma (PTMC). Methods: Bcl-2 protein expression in PTC and PTMC has been evaluated by immunohistochemical analysis. Results: Bcl-2 protein was observed in normal thyroid gland in all the cases; in 25% of the cases of papillary carcinomas the immunoreaction was strong and in 75% of the cases — moderate. In 25% of the cases of papillary microcarcinomas the bcl-2 expression was totally negative and 35% was moderate. Bcl-2 expression was lower in non-sclerosing non–encapsulated (NSNE) (25%) cases of PMCs than in non-sclerosing encapsulated (NSE) (57.15%) cases of PTMCs (p < 0.05). MIB-1/Ki-67 expression was notably reduced or not expressed in normal and benign thyroid tissue. MIB-1 immunoreactivity was present in papillary carcinoma, and on a lower level — in PTMCs. The MIB-1 labelling index of NSE and sclerosing non-encapsulated (SNE) cases was lower than that in NSNE (p < 0.005). Conclusion: The present study indicated that NSNE cases of PTMCs may be an early stage in tumor progression, and the bcl-2 and MIB-1 immunohistochemistry may be a valuable tool in predicting the malignant behavior in PMTCs, and contributes to the understanding the growth characteristics of papillary carcinomas of the thyroid gland.
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