This study was performed to investigate the expression pattern of inducible nitric oxide synthase (iNOS) in osteosarcoma and to determine whether its expression correlates with metastatic potential and prognosis.

Pathologic tissues obtained from 48 patients with primary osteosarcoma were examined immunohistochemically.Stained tissues were categorized into three groups (negative, mild, strong), according to expression intensity, and matched with clinical data. Results were analysed statistically.

iNOS was expressed in 18 of 48 samples (38%). Among the iNOS positive cases, mild expression was observed in 9 patients (18%). There was statistically significant correlation between mild iNOS expression and metastasis (p=0.019). By multivariate analysis mild iNOS expression turned out to be a significant prognostic factor for reduced survival (Risk ratio 4.399, 95% CI 1.694-11.421: p=0.02).

Mild expression of iNOS was significantly related to metastasis in osteosarcoma and can be considered a significant prognostic factor.