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Thymoma and Thymic Carcinoma Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information About Thymoma and Thymic Carcinoma Treatment

Disease Overview

Thymomas and thymic carcinomas are epithelial tumors of the thymus. The term, thymoma, is customarily used to describe neoplasms that show no overt atypia of the epithelial component. A thymic epithelial tumor that exhibits clear-cut cytologic atypia and histologic features no longer specific to the thymus is known as a thymic carcinoma (also known as type C thymoma).[1]

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About This PDQ Summary

Purpose of This Summary This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about endometrial cancer screening. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions. Reviewers and Updates This summary is reviewed regularly and updated as necessary by the PDQ Screening and Prevention...

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Incidence and mortality

Invasive thymomas and thymic carcinomas are relatively rare tumors, which together represent about 0.2% to 1.5% of all malignancies.[2] The overall incidence of thymoma is 0.15 cases per 100,000, based on data from the National Cancer Institute Surveillance, Epidemiology and End Results (SEER) Program.[3] Thymic carcinomas are rare and have been reported to account for only 0.06% of all thymic neoplasms.[4] In general, thymomas are indolent tumors with a tendency toward local recurrence rather than metastasis. Thymic carcinomas, however, are typically invasive, with a higher risk of relapse and death.[5,6]

Age at onset

Most patients with thymoma or thymic carcinoma are aged 40 through 60 years.[7]

Unique disease features

The etiology of these types of tumors is not known. In about 50% of the patients, thymomas/thymic carcinomas are detected by chance with plain-film chest radiography.[7]

Anatomy

Ninety percent of thymomas and thymic carcinomas occur in the anterior mediastinum.[8] They are the most common malignancies of the anterior mediastinum.[9]

Histology

World Health Organization pathologic classification of tumors of the thymus and stage correlate with prognosis.[1] Although some thymoma histologic types are more likely to be invasive and clinically aggressive, treatment outcome and the likelihood of recurrence appear to correlate more closely with the invasive/metastasizing properties of the tumor cells.[1,10] Therefore, some thymomas that appear to be relatively benign by histologic criteria may behave very aggressively. Independent evaluations of both the tumor invasiveness (using staging criteria) and tumor histology should be combined to predict the clinical behavior of a thymoma.

Thymoma and thymic carcinoma should be differentiated from a number of nonepithelial thymic neoplasms, including the following:[1,11]

  • Neuroendocrine tumors.
  • Germ cell tumors.
  • Lymphomas.
  • Stromal tumors.
  • Tumor-like lesions (such as true thymic hyperplasia).
  • Thymic cysts.
  • Metastatic tumors.
  • Lung cancer.

Pathology

Thymoma-associated autoimmune disease involves an alteration in circulating T-cell subsets.[12,13] The primary T-cell abnormality appears to be related to the acquisition of the CD45RA+ phenotype on naive CD4+ T cells during terminal intratumorous thymopoiesis, followed by export of these activated CD4+ T cells into the circulation.[14] In addition to T-cell defects, B-cell lymphopenia has been observed in thymoma-related immunodeficiency, with hypogammaglobulinemia (Good syndrome) and opportunistic infection.[15,16] Patients with thymoma-associated myasthenia gravis can produce autoantibodies to a variety of neuromuscular antigens, particularly the acetylcholine receptor and titin, a striated muscle antigen.[17,18]

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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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