Metastasizing thymoma and myasthenia gravis. Favorable response to glucocorticoids after failed chemotherapy and radiation therapy.

Myasthenia gravis (MG) occurs in up to 44% of patients with thymoma. Thirty-three percent of these neoplasms are invasive but extrathoracic disease is rare. Recently, we saw a patient with MG and recurrent, metastasizing mixed lymphoepithelial thymoma, whose disease was resistant to combination chemotherapy and radiotherapy but who responded dramatically to treatment with daily glucocorticoids. Thus, therapy with daily glucocorticoids should be considered in the treatment of invasive or metastatic thymoma associated with MG, including when conventional surgery, radiotherapy, and chemotherapy have failed.