The expression of nm23-H1, product of putative metastasis suppressor gene, was evaluated immunohistochemically in 31 cases of adenoid cystic carcinoma (ACC) of salivary glands and correlated with their clinicopathologic features. All benign salivary gland tumors of various types, which were used as a non-metastatic control, showed obvious nm23-H1 expression. The immunoreactivity of tumor cells was stronger than that of normal salivary gland components, although the distribution patterns of positive cells considerably varied between tumor types. In ACC, 16 cases (52%) showed the reduction of nm23-H1 immunoreactivity either in positive cell frequency or staining intensity. These cases were referred to as negative cases. The incidence of negative cases was 67% (10/15) and 38% (6/16) of the cases with and without metastasis, respectively. Furthermore, metastatic tumors showed decreased immunoreactivity of this protein compared with their primary tumors. The prognosis of patients with a nm23 negative tumor was generally poorer than that with a positive tumor. These results may suggest that the reduction of nm23-H1 protein has an implication for metastasis of ACC.

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