Myasthenia Gravis and Thymoma Association

Epidemiology and Frequency

Myasthenia gravis (MG) is the most common paraneoplastic autoimmune syndrome associated with thymoma, occurring in approximately 30-50% of patients with thymoma, according to the National Comprehensive Cancer Network 1, 2
One-third of all patients with thymoma present with myasthenia gravis, making it by far the most frequent autoimmune disorder associated with these tumors, as reported by the Annals of Oncology 3, 4
The frequency of MG varies by histological subtype of thymoma, with the highest rates seen in type B2 and B3 thymomas (50% each), followed by type B1 (40%), type AB (20%), and type A (15%), according to the Annals of Oncology 3, 5
Thymic carcinomas are associated with MG in less than 5% of cases, as reported by the Annals of Oncology 3, 5

The presence of myasthenia gravis with an anterior mediastinal mass is highly suggestive of thymoma and should prompt immediate evaluation, according to the Annals of Oncology 5, 6
MG associated with thymoma is almost always accompanied by anti-acetylcholine receptor antibodies, as reported by the Annals of Oncology 3, 4
The combination of MG symptoms (ptosis, diplopia, muscle weakness, dysphagia, dyspnea) with a characteristic anterior mediastinal mass on CT imaging is so specific that surgical biopsy should be avoided if the tumor appears resectable, according to the National Comprehensive Cancer Network 1, 2

Pure red cell aplasia occurs in approximately 5% of thymoma patients, as reported by the Annals of Oncology 3, 4
Hypogammaglobulinemia (Good syndrome) occurs in approximately 5% of cases, according to the Annals of Oncology 3, 4
Other paraneoplastic syndromes collectively occur in less than 10% of patients, as reported by the National Comprehensive Cancer Network 1, 2

When thymoma is suspected, systematic immunological screening is mandatory and should include anti-acetylcholine receptor antibody testing, complete blood count with reticulocytes, serum protein electrophoresis, and anti-nuclear antibodies, according to the Annals of Oncology 5, 6, 7

The presence of autoimmune disorders, particularly MG, significantly impacts all therapeutic interventions including surgery, radiotherapy, and chemotherapy, requiring careful perioperative management, as reported by the Annals of Oncology 5, 6