Acta chir belg, 2005, 105, 644-648 Introduction Homeostasis in multicellular organisms is maintained through the balance between cell proliferation and cell death. Although cell proliferation is widely documented and understood, further studies are needed to understand the details of cell death. Apoptosis, which is considered as an important regulator of cell populations during embryonic development, is a major process of cell death, not only in the immune system but also in normal and neoplastic tissue. Overexpression of mitochondrial bcl-2 is an antidote to this process (1, 2). The bcl-2 gene was originally discovered for its involvement in chromosomal translocations in B cell leukemias and Non-Hodgkin follicular lymphomas (3, 4). The translocation is found in 70% of follicular lym- phomas and 20% of diffuse B cell lymphomas (5). Although mutation of the bcl-2 gene prolongs the cell’s life, it does not have an effect on proliferation (6-8). Lymphocytes’ lives are prolonged in bcl-2 gene trans- ferred mice. Results are similar to squamose and breast cells (1, 2). Bcl-2’s oncogenic potential has been found to be pos- itive in many kinds of epithelial originated malignancies (3, 4, 9-13). Overexpression of the gene is believed to prolong the life of the cell and expose the cell to poten- tial chromosomal abnormalities and viral infections, which may lead to oncogenesis instead of a direct on- cogenic effect (6, 14-16). It has also been proposed that bcl-2 expression might be an early sign of epithelial malignancy (17, 18). The aim of this study was to examine bcl-2 expression in early and advanced stages of papillary thyroid cancers. Material and Methods Thirty-one patients who had undergone a surgical inter- vention for papillary thyroid cancer in Medical Faculty of Istanbul were included in the study. Fifteen patients had papillary thyroid cancers and 16 patients had micro- carcinomas with a diameter of less than 1 cm. The con- tralateral lobes, which are free of any malignant or inflammatory disease such as Graves or Hashimoto’s disease were used as the control samples (n = 31). Expression of bcl-2 in Papillary Thyroid Cancers and its Prognostic Value M. Aksoy*, Y. Giles*, Y. Kapran**, T. Terzioglu*, S. Tezelman* *Department of General Surgery, Medical Faculty of Istanbul University ; **Department of Pathology, Medical Faculty of Istanbul University. Key words. Apoptosis ; papillary cancer ; thyroid cancer ; oncogenesis. Abstract. Purpose : Papillary thyroid cancer has a good prognosis. This favourable prognosis may be attributed to the apoptotic tendency of the cancer cells. This study aims to evaluate the expression of bcl-2, which is an antidote of apop- tosis, and aims to evaluate the value of bcl-2 as a prognostic marker in papillary thyroid cancer. Material-Methods : Bcl-2 expression in the archival materials of 31 patients with papillary thyroid cancer was exam- ined with immunohistochemical methods using bcl-2 and p-53 stains. The results were compared with 31 normal thy- roid tissue specimens, which consisted of the contralateral lobes of these patients. The results were then analyzed in accordance with the clinical features of the patients. Results : Thirty (96.7%) patients of the control group were positive for bcl-2 whilst one (3.3%) was negative. The stain- ing for bcl-2 was positive in 12 (%75) patients with microcarcinomas (p < 0.05) and 13 (86.6%) with papillary cancers (p > 0.05). Two cases of the papillary cancer group were admitted to the hospital with local recurrence (6.4%) and both were positive for bcl-2 (p > 0.05). All cases (4/31), whose MACIS scores were higher than 7 were positive for bcl-2. Twenty-one of 27 cases whose MACIS scores were lower than 7 (77.7%) were positive for bcl-2 (p > 0.05). All tumours of this series were negative for p-53 immunstaining. Conclusion : The rate of bcl-2 expression in microcarcinomas of papillary thyroid cancer decreases when compared to normal thyroid tissue. This may be an early sign of oncogenesis, and a reason for the favourable prognosis in micro- carcinomas. However, bcl-2 cannot be used as a prognostic marker. ————— Sponsored by Research Fund of Istanbul University (Project No. 1037/250897).