Anterior Mediastinal Mass:
Fat: obesity, steroids, lipoma
Tumor:
Thyroid: goiter, adenoma, carcinoma
Lymphoma: (typically Hodgkin's)
Thymic based: thymoma, thymolipoma, thymic
carcinoma, cyst, rebound hyperplasia.
Germ cell neoplasm: teratoma, seminoma,
choriocarcinoma, mixed germ cell.
Metastatic disease
Sarcoma
Lymphangioma: cystic hygroma
Vascular: aneurysm, tortuous vessels
Fluid: hematoma, seroma, pericardial cyst
Various: mediastinitis, Morgagni hernia