As CD9 expression was observed in only one case of sarcomatoid mesothelioma and sarcomatoid histology was itself a strong independent predictor of survival of mesothelioma patients, multivariate analysis excluding sarcomatoid mesothelioma is necessary to evaluate the importance of CD9 expression as an independent predictor of mesothelioma survival. The gene discussed is CD9; the disease is mesothelioma.