Thymoma

In medicine(oncology), thymoma is a neoplasmof the thymus. It is a raredisease, best known for its enigmatic association with the neuromuscular disorder myasthenia gravis. There are benign and malignant forms, which present similarly.

Signs and symptoms

• 33%-50% is detected accidentally on routine X-raysof the chest.
• 33% presents with complaints due to compression of surrounding structures by the expanding tumor:
  • Vena cava superior syndrome(compression of the upper caval vein)
  • Dysphagia(trouble swallowing)
  • Cough, chest pain
• A final 33% has autoimmunesymptoms; thymomas in these are usually benign. The best known is myasthenia gravis, of which 25-50% is associated with a thymoma. Some others are: pure red cell aplasiaand Good's syndrome (thymoma with combined immunodeficiencyand hypoimmunoglobulinemiaG).
  • Rare associations that have been reported are: acute pericarditis, Addison's disease, agranulocytosis, alopecia areata, ulcerative colitis, Cushing's disease, hemolytic anemia, limbic encephalopathy, myocarditis, nephrotic syndrome, panhypopituitarism, pernicious anemia, polymyositis, rheumatoid arthritis, sarcoidosis, scleroderma, sensorimotor radiculopathy, stiff person syndrome, systemic lupus erythematosusand thyroiditis.

Malignant thymomas can metastasize, generally to pleura, kidney, bone, liveror brain.

Diagnosis

When a thymic pass is identified, the diagnosis is achieved with histology(obtaining a tissue sample of the mass). When a thymoma is suspected, a CT/CAT scanis generally performed to estimate the size of the tumor, and can be biopsiedwith a CT-guided needle. Although there is a risk of pneumomediastinum, mediastinitisand the risk of damaging the heartor large blood vessels.

The tumor is generally located inside the thymus, and can be calcified. Increased vascular enhancement can be indicative of malignancy, as can be pleural deposits.

If the suspicion is real, some blood testsare often performed to gain an appreciation of associated problems or possible spread. These include: full blood count, protein electrophoresis, antibodiesto the acetylcholine receptor(indicative of myasthenia), electrolytes, liver enzymesand renal function.

The final diagnosis is made by removing the thymus. Pathologicalinvestigation of the specimen will reveal if the tumor was benign or malignant.

Pathophysiology

Thymomas originate from the epithelialcell population in the thymus. Many subtypes are recognised, some of which have a better- or worse-than-general prognosis.

Epidemiology

Men and women are equally affected. The main age for thymomas is 30-40, although cases have been described in every age group.

Treatment

Surgery is the mainstay of treatment. If the tumor was benign and was removed in its entirety, no further therapy is necessary. Malignant tumors may need additional treatment with radiotherapy, or sometimes with chemotherapy (cyclophosphamide, doxorubicinand cisplatin).

Removal of the thymus in adults does not appear to induce a severe immune deficiency. In children, however, added care and scrupulous vaccination are necessary to protect from infections.

Source

• Thomas CR, Wright CD, Loehrer PJ. Thymoma: state of the art. J Clin Oncol 1999;17:2280-9. PMID 10561285.

External link

• A large resource about thymoma

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Thymoma Wikipedia article Thymoma.