It is actually the most common neoplasm in the entire mediastinum. It usually occurs in adults older than 40 years of age and affects males and females equally. Clinical symptoms include cough, chest pain, dyspnea, weight loss, fever, dysphagia and hoarseness. In most instances, the presence of thymoma is revealed by plain chest roentgenograms. CT scan can confirm the location and may reveal some characteristics of the tumor such as cystic changes or involvement of surrounding structures.
Cut surface is usually grey-tan with bulging and lobulated appearance.
Occasionally, cystic necrosis and calcification can be seen. Microscopically, the tumor typically consists of jigsaw puzzle-type lobules that are separated by fibrous bands. There is an admixture of neoplastic epithelial cells and non-neoplastic lymphocytes in varying proportions. The polygonal epithelial cells usually have bland vesicular nuclei with inconspicuous nucleoli. Another histologic feature seen in two thirds of thymomas is the presence of perivascular spaces, which are formed and bordered by palisading epithelial cells.