• José M Ponseti, Josep Gamez, Ramón Vilallonga, Carmen Ruiz, Jamal Azem, Manuel López-Cano, and Manuel Armengol.
• Department of Surgery, Hospital General Universitari Vall d'Hebron, Autonomous University of Barcelona, Barcelona, Spain. jmponseti@vhebron.net
• Eur J Cardiothorac Surg. 2008 Nov 1; 34 (5): 1062-7.

ObjectiveWe determined the effect of detecting ectopic thymic tissue in thymectomy specimens on the long-term outcome of patients with myasthenia gravis.MethodsA total of 83 consecutive patients with generalized seropositive nonthymomatous myasthenia gravis underwent transsternal extended thymectomy (T-3b according to Myasthenia Gravis Foundation of America). Ectopic thymic tissue was only accepted when Hassal's corpuscles in the excised cervicomediastinal fat were documented. The primary endpoint was to assess differences in time to obtain complete stable remission (CSR) according to the presence or absence of ectopic thymus.ResultsThirty-five patients (42.2%) had ectopic thymic tissue. The mean follow-up was 88.4+/-36.3 months (range 20-144). By the Kaplan-Meier analysis method, the estimated median follow-up to obtain a CSR in the group without ectopic thymic tissue was 32.9 months (95% confidence interval [CI] 21.1-44.8 months) and 117.8 months (95% CI 98.0-137.6 months) for the group with ectopic thymic tissue (log-rank test, p=0.0002). The probability over time of obtaining CSR for the groups without and with ectopic thymic tissue was 65% vs 26% at 5 years. After stratification by hyperplasia or involution of the thymus as well as by post-thymectomy immunomodulating regimen (prednisone and prednisone-tacrolimus), the probability over time of obtaining CSR at 5 years was also significantly higher for patients without ectopic thymic tissue than for those with ectopic thymic tissue.ConclusionsThe clinical outcome of patients with nonthymomatous seropositive myasthenia gravis is significantly affected by the presence of ectopic thymic tissue in the mediastinal fat.

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