Approximately 50% of thymomas are diagnosed when they are localized within a capsule and do not infiltrate.
At the time of diagnosis, the majority of patients with thymoma or thymic carcinoma are asymptomatic. Typical clinical symptoms and signs that are indicative of anterior mediastinal mass effects include the following:
- Signs of upper airway congestion.
Paraneoplastic autoimmune syndromes are associated with thymoma and are rarely associated with thymic carcinomas.[19,20,21]
- Myasthenia gravis is the most common autoimmune disease associated with thymoma. Approximately 30% to 65% of patients with thymoma have been diagnosed with myasthenia gravis in reported series.[22,23]
- Autoimmune pure red cell aplasia and hypogammaglobulinemia are the next most common paraneoplastic syndromes after myasthenia gravis, and affect approximately 5% and 5% to 10%, respectively, of patients with thymoma.
Other autoimmune disorders associated with thymoma include the following:[7,15,24]
- Acute pericarditis.
- Addison disease.
- Cushing syndrome.
- Hemolytic anemia.
- Limbic encephalopathy.
- Nephrotic syndrome.
- Pernicious anemia.
- Aplastic anemia.
- Sensorimotor radiculopathy.
- Sjögren syndrome.
- Stiff-person syndrome.
- Systemic lupus erythematosus.
- Ulcerative colitis.
Prognosis and Survival
Although the oncologic prognosis of thymoma is reported to be more favorable in patients with myasthenia gravis than in patients without myasthenia gravis,[8,25] data are conflicting as to whether the presence of myasthenia gravis is an independent predictor of better outcome. Patients with myasthenia gravis are diagnosed with earlier stage disease and more often undergo complete surgical resection. Treatment with thymectomy may not significantly improve the course of thymoma-associated myasthenia gravis.[26,27]
Thymoma has been associated with an increased risk for second malignancies. In a review of the SEER database of thymoma cases in the United States between 1973 and 1998, 849 cases were identified (overall incidence 0.15 per 100,000 person-years). In this study, there was an excess risk of non-Hodgkin lymphoma and soft tissue sarcomas.
Risk of second malignancy appears to be unrelated to any of the following:[3,27,28]
- A clinical history of myasthenia gravis.
Standard primary treatment for patients with these types of tumors is surgical resection with en bloc resection for invasive tumors, if possible.[5,7,8,29] Depending on tumor stage, there are multimodality treatment options, which include the use of radiation therapy and chemotherapy with or without surgery.[7,30]
Thymic carcinomas have a greater propensity to capsular invasion and metastases than thymomas. Patients more often present with advanced disease, with a 5-year survival of 30% to 50%. Owing to the paucity of cases, optimal management of thymic carcinoma has yet to be defined. As with thymoma, primary treatment is surgical resection; however, multimodality treatment with surgery, radiation, and chemotherapy are often used because of the more advanced stage and greater risk of relapse.