Objective To investigate the activation and significance of nuclear transcription factorκB (NFκB) in primary breast carcinoma. MethodsImmunohistochemical staining method was used to detect expression of NFκB in 28 cases of primary breast carcinoma and 21 cases of breast tissues closely adjacent to carcinoma tissues. ResultsIt showed that there was expression of NFκB in 28 cases of breast carcinoma tissues and 21 cases of breast tissues closely adjacent to carcinoma. In 21 cases of breast tissues closely adjacent to carcinoma, NFκB was localized mainly in cytoplasm of epithelium cells of ducts and lobular acini. In 28 cases of breast carcinoma NFκB was mainly expressed in cytoplasm and /or nuclei of breast carcinoma cells. Conclusion NFκB is expressed in breast tissues closely adjacent to carcinoma and primary breast carcinoma tissues, and the expression style in the two situation was different. In the breast tissues closely adjacent to carcinoma, NFκB is localized in cytoplasm of epithelium cells of breast acini and duct in an inactive state. In breast carcinoma tissues, NFκB is localized in both cytoplasm and nuclei of carcinoma cells. This study suggests that NFκB is activated in breast carcinoma and plays a significant role in its tumorigenesis and development.