Significant increased expression of CCL25 was noticed in 80% (20/25) cases of thymoma with MG, while only one case of thymoma without MG that had overexpression of CCL25, which suggested that overexpression of CCL25 gene in thymoma might play a vital role in the pathogenesis of myasthenia gravis. The gene discussed is CCL25; the disease is myasthenia gravis.