Definition, Etiology, Clinical FeaturesTop
Mediastinal cysts and tumors are usually detected incidentally on imaging or when investigating nonspecific complaints regarding a variety of structures in this area.
1) Anterior mediastinal mass: Incidental anterior mediastinal lesions originate most frequently from the structures known as the 4 T’s: thymus, thyroid, teratoma, and T-cell lymphoma. The most common thymic lesions are hyperplasia, cysts, and thymomas. Germ cell tumors include teratoma (most common), seminoma, nonseminomatous germ cell tumor, choriocarcinoma, and embryonal carcinoma. Other causes of anterior mediastinal mass include parathyroid adenoma, lymphoproliferative neoplasms, mesenchymal tumors, lipoma, liposarcoma, angiosarcoma, leiomyoma, and watery cysts (mediastinal lymphangioma).
2) Middle mediastinal mass: Lymphadenopathy: lymphoma, granulomatous disease (sarcoidosis, tuberculosis, silicosis, fungal infection); metastases of neoplasms of other organs; cysts: pericardial cysts, bronchial cysts; vascular lesions: aortic aneurysm, brachiocephalic trunk aneurysm, congenital vascular malformations; diaphragmatic hernia.
3) Posterior mediastinal mass: Neurogenic tumors; esophageal diseases: achalasia, cysts, cancer, diverticulum; lateral thoracic meningocele; thoracic duct cysts.
Symptoms: Most mediastinal tumors are asymptomatic. Symptoms are caused by mass effect and compression of other organs. They may include dyspnea, cough, stridor, continuous or periodic chest pain (referred to the chest wall), dysphagia, neuralgia, other neurologic symptoms (caused by compression of the spinal cord by a neurogenic tumor), and superior vena cava syndrome.
Chest radiography and computed tomography (CT), differentiation from metastases (of breast, lung, or gastric cancers), search for the primary lesion when necessary (in men examine the testes!), mediastinoscopy, and biopsy.
Imaging studies: Cystic lesions are commonly of thymic origin. Magnetic resonance imaging (MRI) is often useful for distinguishing between cysts and solid masses, particularly in posterior compartment masses, and for identifying necrosis and septations. Endoscopic ultrasonography is also helpful in differentiating cystic lesions from solid lesions and for collecting biopsy specimens. For noncystic lesions, if biopsy or surgery is not immediately decided upon, follow-up CT after 3 to 6 months is generally recommended to assess disease progression.
Tumor markers that should be considered:
1) Thymic masses: Acetylcholine receptor antibodies.
2) Suspected germ cell tumor: Alpha-fetoprotein (AFP) (ovarian and testicular germ cell tumor) and beta human chorionic gonadotropin (beta-hCG) (suspected choriocarcinoma).
3) Suspected germ cell tumor or lymphoma: Lactate dehydrogenase (LDH).
Presence of an undiagnosed mediastinal mass usually requires consultation with a thoracic surgeon. For suspicious anterior mediastinal masses that are resectable, resection without biopsy is preferred to avoid tumor seeding. Core biopsy should be obtained whenever possible if it affects management (eg, if a lymphoma is suspected and the management is nonsurgical).