Fact-sheet: Thymoma
Updated on 09/17/2021 at 12:16 PM
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Definition
Thymic tumor, most often benign (60-70%).
Can be malignant, most often locally invasive with rare distant metastases.
Clinical features
Mean age: around fifty.
Can be asymptomatic and incidentally discovered (chest X-ray)
Cough, dyspnea, pleuritic pain, or superior vena cava syndrome
Myasthenia gravis
Hematologic abnormalities (neutropenia, erythroblastopenia)
Neurologic syndrome or paraneoplastic encephalitis
Radiography
Anterior mediastinal mass, of soft-tissue density
Sometimes calcified
CT
- Anterior mediastinal soft-tissue mass
- Benign thymoma: encapsulated
- Malignant thymoma: irregular margins. Locoregional extension to the mediastinal fat, pericardium, mediastinal vessels, heart, lung parenchyma. Pleural involvement very common.
- If bronchiectasis present: Good syndrome.
Differential diagnosis
Anterior mediastinal masses:
- Solid thymic lesions
- Solid teratoid lesions: Teratoma, embryonal cell carcinoma, choriocarcinoma, seminoma.
- Thyroid/parathyroid lesion: plunging goiter, thyroid carcinoma or adenoma, ectopic parathyroid adenoma
- Adenopathy: Lymphoma, metastasis, benign lymphatic hyperplasia, angioblastic lymphadenopathy, mediastinal lymphadenitis of sarcoidosis or a granulomatous infection.
- Cardiovascular
- Cystic lesion: Cystic hygroma, bronchogenic cyst, extralobar sequestration, thymic cyst, dermoid cyst, pericardial cyst, pancreatic pseudocyst.
- Other: Nerve sheath tumor, paraganglioma, hemangioma/lymphangioma, sternal tumor, mediastinal invasion by a lung or pleural tumor, mediastinal lipomatosis, Morgagni hernia, abscess.
Pleural involvement in thymoma can mimic mesothelioma.