Thymoma and Thymic Carcinoma: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Thymoma and thymic carcinoma are rare thymic epithelial tumors, accounting for less than 1% of thoracic malignancies. Thymoma is the most common primary thymic tumor (~60%) and is generally indolent. Thymic carcinoma is more aggressive. Both occur predominantly in adults aged 40-60 years presenting with anterior mediastinal masses.

The majority are sporadic with no established environmental risk factors. Thymoma is uniquely associated with autoimmune paraneoplastic conditions, most notably myasthenia gravis (in 30-45% of thymoma patients). Chromosomal alterations including GTF2I mutation in type A/AB thymomas are common. Thymic carcinoma harbors KIT and other oncogenic mutations.

Many are detected incidentally on chest imaging. Symptoms include chest pain, cough, and dyspnea from mediastinal mass effect. Myasthenia gravis (MG): ptosis, diplopia, bulbar weakness, proximal muscle weakness, and respiratory failure. Superior vena cava syndrome in advanced disease. Constitutional symptoms (fever, weight loss) more common with thymic carcinoma.

CT chest with contrast is primary imaging. MRI for vascular and pericardial involvement assessment. CT-guided or thoracoscopic (VATS) biopsy for tissue diagnosis. Masaoka-Koga surgical staging (I-IVb) is the primary staging system. WHO histological classification (types A, AB, B1, B2, B3, and TC). Anti-acetylcholine receptor antibodies and pyridostigmine testing for myasthenia gravis.

Complete thymectomy is the cornerstone of treatment and also improves myasthenia gravis control. Adjuvant radiotherapy for incompletely resected (R1/R2) or Masaoka Stage III/IV thymoma. Cisplatin-based chemotherapy (CAP: cisplatin, doxorubicin, cyclophosphamide; or carboplatin/paclitaxel) for unresectable or metastatic disease. Pembrolizumab is FDA-approved for unresectable or metastatic thymic carcinoma. Lenvatinib and sunitinib show activity in refractory thymoma.

Thymoma Masaoka Stage I: 5-year OS approximately 95-100%. Stage II: approximately 85-90%. Stage III: approximately 70%. Stage IVa/b: approximately 50%. Complete surgical resection is the most important prognostic factor. Thymic carcinoma: 5-year OS approximately 30-50% even after resection, reflecting its more aggressive biology compared to thymoma.