The present study found that the loss of CD9 expression in mesothelioma is related to a shorter overall survival (medial survival 9 months, 1-year survival 38.9% and 2-year survival 11.1%) compared to patients with CD9 expression (median survival 15.1 months, 1-year survival, 63.2% and 2-year survival 25%). This evidence concerns the gene CD9 and mesothelioma.