Epidemiology

• Most common cause of anterior mediastinal mass in adults
• Age: usually develop between 40-60 y/o
• Sex: occur equally among men and women
• Associated With:
  • Myocarditis
  • Hypogammaglobulinemia
  • Cushing s Syndrome
  • Megaesophagus
  • Myasthenia Gravis:
  • Pure Red Cell Aplasia:

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Physiology

• Typically develop adjacent to the junction of the heart and great vessels and tend to be round or oval in shape with relatively smooth margins
• Myasthenia Gravis: the mechanism of thymoma-related myasthenia gravis is thought to be thymic production of autoantibodies directed at acetylcholine receptors

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Diagnosis

• CXR/Chest CT patterns
• I131 Scan: negative (excludes thyroid as cause of an anterior mediastinal mass)

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Clinical

Symptoms/Signs:
-Sixty percent of patients may be asymptomatic at time of diagnosis; other vague symptoms include cough, dyspnea, and/or chest pain
-Malignancy is best defined by the degree of invasiveness found at surgery, not by histologic appearance
-Benign thymomas (55% to 65%) are contained within a thick fibrous capsule and are cured at time of surgical remova
-Myasthenia Gravis: occurs in 10% to 50% of patients with thymomas, either benign or malignant
-Pure Red Cell Aplasia:
–About 50% of patients with pure red cell aplasia have a thymoma
–Only 5% of patients with thymoma have pure red cell aplasia.

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Treatment

• Malignant Thymoma: invade through the capsule and spread locally, and are treated with surgery followed by postoperative radiation
  • Thymectomy may induce remission of Pure Red Cell Aplasia in 50% of cases and improvement in Myasthenia Gravis

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References

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