Immunohistochemical demonstration of the nm23-H1 gene product in human malignant melanoma and Spitz nevi

Expression of the 17 kD product of the human nm23-H1 gene has been shown to be reduced in a number of human malignancies including those from the breast, colon, kidney and lung. Somatic allelic deletion of nm23-H1 gene is also associated with a high incidence of distant metastasis and reduced patient survival in colorectal and infiltrating breast ductal carcinomas. We compared the immunohistochemical reactivity of the nm23-H1 gene product in the different histological subtypes of human cutaneous melanoma to that of Spitz nevi. All nine cases of Spitz nevi and five cases of in situ melanoma showed diffuse and intense nm23-H1 protein immunoreactivity. The majority of superficial spreading melanomas (18 of 27 cases) had moderate to strong nm23-H1 protein immunostaining. In contrast, the majority of nodular melanomas (7 of 8 cases) with poor prognostic histological indices displayed marked reduction in immunoreactivity to the nm23-H1 protein. The 2 cases of metastatic melanoma showed reduced or no nm23-H1 protein immunostaining. In conclusion, reduced nm23-H1 immunohistological expression is associated with melanomas that have high metastatic potential and poorer prognosis.