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Abstract
The thymus gland consists of two lateral lobes placed in close contact along the middle line between the lungs in the anterior superior mediastinum extending from the fourth costal cartilage upward, as high as the lower border of the thyroid gland (Miller, 2002).The thymic tumors are divided into five categories according to the type of cells of origin:
I -Thymic epithelial tumors(thymoma and thymic carcinoma). 2-Thymic neuroendocrine tumor.
3-Thymic germ cell tumors(teratomas, seminomas, embryonal carcinoma, yolk sac tumors and choriocarcinoma).
4-Thymic lymphoma(Hodgkin and non Hodgkin).
5-Thymolipoma. (Cameron et aL, 2000).Symptoms of thymic tumors are often absent, and the tumor may be discovered incidentally on routine chest roentgenograms in the majority of patients (Hudson et aL, 1995).
Benign tumors and cysts can produce compression or obstruction of portions of the airway, the esophagus, or the right heart and great veins. Malignant thymic tumors can produce abnormalities by invasion of local structures such as the tracheobronchial tree, lungs, esophagus, superior vena cava, pleura, chest wall, and any adjacent intrathoracic nerves.