Prognosis in occult thymomas in myasthenia gravis following transcervical thymectomy.

Thymomas were noted in 239 (11%) of 2097 myasthenic patients followed up at our institution. Among 996 patients who had undergone thymectomy, 191 patients (19%) had thymomas compared with 48 (4%) of 1101 patients treated without surgery. A definitive diagnosis of thymoma was not made until after thymectomy in 61 patients (35%); in patients not treated with thymectomy, 23% of associated tumors were diagnosed at autopsy. Patients with occult thymomas treated with the transcervical approach had a clinical course superior to those with tumors diagnosed prior to surgery and treated with the transsternal approach. Most of the advantage could be attributed to the association of occult thymomas with small tumor size and to the association of the latter with absence of invasiveness. Small tumor size was significantly associated with higher remission and lower mortality as shown in a proportional hazards analysis. Occult thymomas were accessible through the transcervical approach, with some operations necessitating a complementary mediastinotomy. Thymectomy, through the transcervical approach if technically feasible, is of benefit to all patients, has minimal morbidity, and should be performed early in the course of the disease as a diagnostic and therapeutic intervention since the risk of occult thymomas in patients with myasthenia gravis is high.