Objectives: to investigate immunohistochemically localization pattern and distribution of
inducible Nitric Oxide Synthase (iNOS) in pleomorphic adenoma (PA ) of salivary glands and to
find a correlation of its expression with Cyclooxygenase-2 (COX -2) and tumor proliferative activity.
Material and Methods: 18 cases of PA were subjected to immunohistochemical staining
for iNOS, COX-2 and proliferative cell nuclear antigen (PCNA) using streptavidin-peroxidase
technique. 10 samples of normal salivary glands tissues (NSG) were used as a control. COX-2,
iNOS and PCNA expression were statistically compared.
Results: in PA , expression of iNOS was increased as that of COX-2 when compared with
the control. The expression intensity and pattern of distribution of studied proteins were different
within the tumor tissue. The strong expression was localized mainly at the tumor periphery while
the center of tumor showed weak or even negative expression. The PCNA-LI mean percentage was
higher in the periphery of the tumors. The low expression scores of iNOS were detected in 4 cases,
moderate in 5 cases and high in 7 cases, whereas the expression scores of COX-2 were observed in
5 cases (low), in 9 cases (moderate) and 5 cases (high). The expression scores of iNOs and COX-2
were significantly correlated (P≤0.05). Significant correlation of expression scores of COX -2 and
iNOS with PCNA-LI (P≤0.01) were found.
Conclusion: this study revealed that COX -2 and iNOS expression was increased significantly
in PA . Their pattern of expression was more in the periphery of the lesion than the center. The
labelling index of PCNA was higher in the periphery of the lesion indicating that the tumorous
and proliferative activity of PA is more at tumor tissues near the margins suggesting that the
aggressiveness of PA is at the tumor peripheries.