The B-type Raf kinase (BRAF) is a member of RAS\RAF\MEK\ERK pathway and this pathway can lead to increased cellular growth, invasion and metastasis. The mutated BRAF protein activates MAPK signaling pathway, results in abnormal cellular growth, apoptosis resistance, tumor progression and metastasis. Pan-BRAF is one of available BRAF monoclonal antibodies and shared by both the wild and mutant BRAF.BRAF status is mostly determined by DNA sequencing methods. In this investigation we assessed the monoclonal Pan BRAF specific antibody that can identify wild and mutant type proteins together in formalin-fixed paraffin-embedded thyroid tumor tissues by Immunohistochemistry (IHC). Archival thyroid samples from 43 iraqi patients were immunohistochemically tested with antibodies for BRAF. Out of 43 thyroid tissue cases, (23) were thyroid malignant,(12) benign, and (8) control cases(diagnosed as colloid goiter).The malignant tumors included Papillary Thyroid Carcinoma (PTC), Follicular Thyroid Carcinoma (FTC), Medullary Thyroid Carcinoma (MTC), Anaplastic Thyroid Carcinoma (ATC) and Hürthle cell cancer (HCC).Immunohistochemical staining for BRAF was performed for all specimens. Results of the study showed that Immunohistochemical expression of pan BRAF was significantly higher in malignant thyroid tumors as compared with adenomas and control cases (P<0.05). BRAF over-expression was detected in 5\12 of PTC, 3\5 MTC, 2\4 of FTCas well as all cases of HCC, ATC.Whereas it was detected in 4\12 of adenomas, and totally negative in control cases. No association was observed between BRAF and other clinicopathological traits. We conclude from this study that IHC using BRAF monoclonal antibody is a
successful way for checking of BRAF status in different thyroid tumors. IHC may be the alternative to molecular biology for the routine detection of this marker in patients with thyroid tumors.
