| Thymoma | |
|---|---|
 | |
| An encapsulated thymoma (mixed lymphocytic and epithelial type) | |
| Specialty | Oncology,cardiothoracic surgery |
| Usual onset | Adulthood |
| Treatment | surgical removal,chemotherapy (in malignant cases). |
Athymoma is atumor originating from theepithelial cells of thethymus that is considered a rare neoplasm.[1] Thymomas are frequently associated with neuromuscular disorders such asmyasthenia gravis;[2] thymoma is found in 20% of patients with myasthenia gravis.[3] Once diagnosed, thymomas may be removed surgically. In the rare case of a malignant tumor,chemotherapy may be used.
A third of all people with a thymoma have symptoms caused by compression of the surrounding organs by an expansive mass. These problems may take the form ofsuperior vena cava syndrome,dysphagia (difficulty swallowing),cough, orchest pain.[2]
One-third of patients have their tumors discovered because they have an associatedautoimmune disorder. As mentioned earlier, the most common of those conditions ismyasthenia gravis (MG); 10–15% of patients with MG have a thymoma and, conversely, 30–45% of patients with thymomas have MG. Additional associated autoimmune conditions includethymoma-associated multiorgan autoimmunity,pure red cell aplasia andGood syndrome (thymoma withcombined immunodeficiency andhypogammaglobulinemia). Other reported disease associations are withacute pericarditis,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 erythematosus andthyroiditis.[2][4]
One-third to one-half of all persons with thymoma have no symptoms at all, and the mass is identified on achest X-ray orCT/CAT scan performed for an unrelated problem.[2]
Thymoma originates from theepithelial cell population in the thymus, and several microscopic subtypes are now recognized.[2] There are three principal histological types of thymoma, depending on the appearance of the cells by microscopy:
Thymic cortical epithelial cells have abundant cytoplasm, vesicular nucleus with finely divided chromatin and small nucleoli and cytoplasmic filaments contact adjacent cells.Thymic medullary epithelial cells in contrast are spindle shaped with oval dense nucleus and scant cytoplasmthymoma if recapitulates cortical cell features more, is thought to be less benign.
When a thymoma is suspected, aCT/CAT scan is generally performed to estimate the size and extent of the tumor, and the lesion is sampled with a CT-guided needlebiopsy. Increased vascular enhancement on CT scans can be indicative of malignancy, as can be pleural deposits.[2] Limited[clarification needed] biopsies are associated with a very small risk ofpneumomediastinum ormediastinitis and an even-lower risk of damaging theheart or large blood vessels. Sometimes thymoma metastasize for instance to the abdomen.[6]
The diagnosis is made via histologic examination by a pathologist, after obtaining a tissue sample of the mass. Final tumor classification and staging is accomplished pathologically after formal[clarification needed] surgical removal of the thymic tumor.
Selected laboratory tests can be used to look for associated problems or possible tumor spread. These include:full blood count,protein electrophoresis,antibodies to theacetylcholine receptor (indicative of myasthenia),electrolytes,liver enzymes andrenal function.[2]
The Masaoka Staging System is used widely and is based on the anatomic extent of disease at the time of surgery:[7]
Surgery is the mainstay of treatment for thymoma. If the tumor is apparently invasive and large, preoperative (neoadjuvant) chemotherapy and/or radiotherapy may be used to decrease the size and improve resectability, before surgery is attempted. When the tumor is an early stage (Masaoka I through IIB), no further therapy is necessary. Removal of the thymus in adults does not appear to induceimmune deficiency. In children, however, postoperative immunity may be abnormal and vaccinations for several infectious agents are recommended. Invasive thymomas may require additional treatment with radiotherapy and chemotherapy (cyclophosphamide,doxorubicin andcisplatin).[2][citation needed].[8] Recurrences of thymoma are described in 10-30% of cases up to 10 years after surgical resection, and in the majority of cases also pleural recurrences can be removed. Recently, surgical removal of pleural recurrences can be followed by hyperthermic intrathoracic perfusion chemotherapy orintrathoracic hyperthermic perfused chemotherapy (ITH).[9]
Prognosis is much worse for stage III or IV thymomas as compared with stage I and II tumors. Invasive thymomas uncommonly can alsometastasize, generally topleura,bones,liver orbrain in approximately 7% of cases.[2] A study found that slightly over 40% of observed patients with stage III and IV tumors survived for at least 10 years after diagnosis. The median age of these patients at the time of thymoma diagnosis was 57 years.[10]
Patients who have undergone thymectomy for thymoma should be warned of possible severe side effects after yellow fever vaccination. This is probably caused by inadequate T-cell response to live attenuated yellow fever vaccine. Deaths have been reported.[citation needed]
The incidence of thymomas is around 0.13-0.26 per 100,000 people per year.[11] Males are affected slightly less frequently than females.[11] The typical age at diagnosis is in the 40s and 50s, though the age may range from six years to 83 years.[11]
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Authority control databases: National |
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