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Anterior mediastinal compartment, also known as anterosuperior compartment, is anterior to the pericardium. Masses in this area is more likely to be malignant than those in other compartments (1) Most common masses found here include thymomas, germ cell tumors, lymphomas, thyroid tissue, and parathyroid lesions.
Thymoma
Most common primary anterior mediastinal tumor (20%) in adults but rarely seen in children. It can be classified as lymphocytic, epithelial, or spindle cell histologies, but this is not very significant clinically (2). Tonofibrils seen under electron microscopy can differentiate thymoma from other tumors such as carcinoid, Hodgkin's, and seminoma. Patients are usually asymptomatic but can present with myasthenia gravis-related symptoms, substernal pain, dyspnea, or cough. Invasive tumors can produce compression effects such as superior vena cava syndrome. (3,4) Thymomas are diagnosed with CT or MRI revealing mass in anterior mediastinum. Therapy in stage I tumors consists of surgical ressection with good prognosis. Stage II-III requires maximal resection possible followed by radation. Stage IV disease requires addition of cisplatin-based chemotherapy in addition to those in stage II and III. For those with invasive thymoma, treatment is based on induction chemotherapy, surgical resection, and post-surgical radiation. 5-year survival for invasive thymoma is between 12-54% regardless of any myasthenia gravis symptoms (5,6).
Lymphoma
Secondary most common primary anterior mediastinal mass in adults. Most are seen in the anterior compartment and rest are seen in middle compartment. Hodgkin's usually present in 40-50's with nodular sclerosing type (7), and non-Hogdkin's in all age groups. Can also be primary mediastinal B cell lymphoma with poor prognosis (8,9). Common symptoms include fever, weight loss, night sweats, and compressive symptoms such as pain, dyspnea, wheezing, SVC syndrome, pleural effusions (10,11). Diagnosis usually by CT showing lobulated mass. Confirmation done by tissue biopsy of accompanying nodes if any, mediastinoscopy, mediastinotomy, or thoracotomy. FNA biopsy usually not adequate. (12,13,14) Treatment of mediastinal Hodgkin's involves chemotherapy and/or radiation. 5 year survival is now around 75%. Mediastinal non-Hodgkin's only has median survival of 13 months even with chemotherapy and radiation. (15) Large-cell type may have somewhat better prognosis. Surgery is generally not performed because of invasive nature of tumor.
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