Primary thymic tumours

Most common masses of the anterior mediastinum

Thymomas

• Presentation
  • Half present with paraneoplastic syndrome
    • Myaesthenia gravis
    • Red cell aplasia
    • Hypogammaglobulinaemia
  • Cough
  • Local compressive symptoms
  • Incidental
• Imaging
  • Well-defined solid or cystic soft tissue mass within the anterior mediastinum. Generally occurs within normal thymic area in upper substernal area.
  • CT is diagnostic
  • MRI adds clarity, and assesses for invasion
    • If invasion, consider thymic carcinoma (WHO type C thymoma)
    • This patient would need PET scan, biopsy, and neoadjuvant chemoradiotherapy
• Histopathology
  • Types of thymic tumours:
    • Thymomas
      • No atypia or mitotic activity
    • Atypical thymomas/well-differentiated thymic carcinomas
    • Thymic carcinomas
• Staging

• 5 year survival based on Masaoka-Koga staging:
  • 1: 95%
  • 2: 80%
  • 3: 65%
  • 4a: 50%
  • 4b: <50%

• Treatment
  • R0 surgical resection is optimal for all thymic tumours
    • Mainstay of treatment for thymoma
    • Excellent long-term outcomes (90% 5 year survival if completely resected)
    • May entail extensive resection of surrounding structures
    • Entire thymus should be resected in continuity with the tumour, along with attached mediastinal fat
  • Adjuvant RTX may prevent local recurrence, especially if incomplete resection
• Surgical approach
  • Can be either open or minimally-invasive (VATS vs robot)
    • VATS only works with smaller, easily removable tumours
  • Transcervical thymectomy is not appropriate for thymic tumours