The role of nuclear factor (NF)-кBp65 pathway in the pathogenesis of follicular thyroid carcinoma (FTC) has not been fully investigated. We retrieved 10 cases of FTC from our file. Tissue microarrays (TMAs) were constructed using 2.0 mm cores from formalin-fixed, paraffin-embedded tissue blocks. TMA sections were immunohistochemically stained for phosphorylated (p)-NF-кBp65 (Ser 536), cyclooxygenase-2 (COX-2), IL-8, and glutathione S-transferase (GST)-pi. Staining intensity (0-3+), extensiveness (0-100%) and subcellular compartmentalization were evaluated. Both nuclear and cytoplasmic immunoreactivities with p-NF-кBp65 (Ser 536) antibodies were observed in all 10 cases, including moderate to strong nuclear staining intensity with a range of extensiveness in 20% - 100% of tumor cells. Moderate (2+) or strong (3+) cytoplasmic expressions of COX-2 and IL-8 were present in 60-100% and 50- 100% of tumor cells, respectively, in all cases. GST-pi was diffusely (70-100%) and moderately or strongly staining the tumor cytoplasm in all cases (except one case with insufficient tissue) with three of them demonstrating nuclear positivity as well. Morphoproteomic analysis reveals the constitutive activation of the NF-кBp65 pathway in follicular thyroid carcinomas as evidenced by phosphorylation at Ser 536 with nuclear translocation and with correlative expression of transcriptionally activated gene products (COX-2, IL-8, and GST-pi). This observation may provide a molecular basis for the tumor biology and targeted therapies for follicular thyroid carcinoma.