Prognostic factors of oral mucosal melanoma: histopathological analysis in a retrospective cohort of 82 cases

Aims: To investigate the histopathological predictors of overall survival and metastatic failure of oral mucosal melanoma (OMM), of which the histopathological classification and microstaging has not been established. Methods and results: The pathological data, including cell type (CT), level of invasion, ulceration, mitotic rate, pigmentation, necrosis, tumour-infiltrating lymphocyte (TIL) and vascular invasion, of 82 OMM patients from April 2002 to April 2012 were reviewed and analysed retrospectively. CT, ulceration, mitotic rate, pigmentation, necrosis and vascular invasion were found to be of significance in predicting the overall survival of OMM patients. CT was an independent prognostic factor of overall survival in multivariate analysis. In patients with localized OMM, CT, level of invasion, mitotic rate, pigmentation and necrosis were associated with overall survival but none of them proved to be an independent prognostic factor. CT, mitotic rate and TIL were associated with the risk of distant metastasis. TIL was revealed to be an independent factor of distant metastases risk in multivariate analysis. Conclusions: CT was an independent prognostic factor of overall survival. Patients with epithelioid cell type OMM had a poor prognosis. Patients without TIL had a higher risk of distant metastasis.