Background: The diversity of salivary gland malignancies as to morphology and clinical course makes it difficult to establish prognostic factors. The aim of this study was to evaluate the prognostic significance of, a. o., immunohistochemical criteria in a retrospective study of salivary gland cancer.
Patients and methods: Clinical and histologic data were recorded for 101 patients with carcinomas of the salivary glands. Immunohistochemistry was performed for Ki-67, P53, C-KIT, HER2, EGFR, and maspin. Correlations to disease-specific long-term survival (mean follow-up 4.7 years) were followed by univariate and multivariate analysis.
Results: Findings included the following: an association between loss of maspin and the presence of nodal metastasis, residual tumour, and poor overall survival for adenoid cystic carcinoma; common C-KIT expression in adenoid cystic carcinoma (92%); correlation of loss of C-KIT with high malignancy grade, nodal metastases, high proliferative activity (Ki-67>30%), and unfavourable survival in all tumours; common HER2 expression (83%) in salivary duct carcinoma but no relation to the total collective's survival. Overexpression of EGFR was associated with poor survival rates. In multivariate analysis, a high proliferation index was the strongest predictive factor, followed by the presence of residual tumour, overexpression of EGFR, and advanced clinical stage.
Conclusions: The clinical stage is of higher prognostic value than histology and grade of malignancy. High proliferative activity (Ki-67>30%) is the strongest negative predictor in salivary gland cancer. Besides well-known clinicopathological factors, current immunohistochemical markers such as maspin, EGFR, and C-KIT can contribute to establish prognosis in salivary gland cancer.