A thymoma is a tumor arising from thymic epithelial cells. It is usually benign and may be referred to as a lymphoepithelioma when it contains many lymphoid cells. Thymomas are usually encapsulated and rarely metastasize. They are believed to be the cause of some paraneoplastic syndromes because of their disruption of the selection and maturation process of T lymphocytes. The following steps will show how to diagnose a thymoma.
Expect a variety of symptoms from thymomas. One third of patients will be asymptomatic and diagnosed incidentally from a chest radiograph. One third will have only local symptoms caused by compression of the thymoma into adjacent structures and one third will present with myasthenia gravis (MG.)
Observe clinical signs such as immunodeficiency disorders and paraneoplastic syndromes, including red blood aplasia, hypogammaglobulinemia and MG. Patients with Good syndrome may have recurrent bacterial, fungal and viral infections.
Conduct laboratory studies to assess the effect of the thymoma. A complete blood count should show anemia, granulocytopenia and thrombocytopenia. Immunoglobulin levels should be checked routinely because patients with thymoma usually have Panhypogammaglobulinemia. The CD4+ T-cell count also will be low and the B-cell count will be low or even absent.
Use a Computed Tomography (CT) scan or Magnetic Imaging Resonance (MRI) to define the mass and identify the presence of cysts, fat or necrosis. Imaging with radioactive tracers also has proven useful.
Determine the histology of the thymoma. These have traditionally been classified into the four non-specific categories based on the number of lymphocytes and the shape of the epithelial cells: epithelial thymoma, lymphocytic, mixed lymphocytic, and epithelial and spindle cell.