An immunohistochemical analysis to evaluate an inverse correlation between Runx2/Cbfa1 and NF kappa B in human osteosarcoma. Dominant negative inhibition of nuclear factor kappa B (NF kappa B) signalling activity in a human osteosarcoma cell line (Saos2) results in malignant reversion and the induction of the osteoblast differentiating transcription factor, Runx2/Cbfa1. This observation suggests that there is an inverse relation between a transcription factor associated with malignant progression and chemoresistance (NF kappa B) and an osteoblast differentiating transcription factor (Runx2/Cbfa1).To assess and correlate Runx2/Cbfa1 and NF kappa B (p65) immunoreactivity in human osteosarcoma.Runx2/Cbfa1 and NFkappaB (p65) immunoreactivity was assessed on 11 paraffin wax embedded archival specimens of human primary osteosarcoma by standard immunohistochemical methods and scored on a scale of 0-3. A Pearson correlation analysis between Runx2/Cbfa1 and NF kappa B (p65) scores was established.Runx2/Cbfa1 was expressed constitutively in all pathology specimens of human osteosarcoma. Of note, a chondroblastic osteosarcoma showed the highest Runx2/Cbfa1 immunoreactivity. A Pearson correlation did not support an inverse correlation between Runx2/Cbfa1 and NF kappa B (p65) scores (r = 0.57) in human osteosarcoma.Runx2/Cbfa1 immunoreactivity does not inversely correlate with NF kappa B immunoreactivity, and thus cannot serve as an indirect measure of NF kappa B activity or an independent predictive or prognostic indicator.