• Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

Cancer 101: Cancer Explained

What causes thymoma, and what are risk factors for thymoma?

The exact cause of thymomas is not known. Thymomas are slightly more common in men than in women and are most frequently seen in persons between the ages of 40 and 60. There are no known risk factors that predispose a person to developing thymoma.

What are signs and symptoms of thymoma?

Up to 50% of thymomas are asymptomatic, meaning they do not produce any symptoms or signs and are diagnosed when an imaging study is performed for another reason. In other cases, the tumor may cause symptoms related to the size of the tumor and the pressure it exerts on adjacent organs. Chest pain, shortness of breath, and cough are common symptoms when symptoms do occur. Fever, night sweats, and weight loss are less common but may occur. Some cases may spread to the lining of the lungs or heart or even to tissues outside the chest. Less than 7% of cases are accompanied by spread outside the chest cavity. Thymic carcinomas are more aggressive tumors than thymomas and are more likely to spread both locally and distantly (metastasize) and to cause symptoms.

What other medical conditions are associated with thymoma?

A number of conditions have been associated with thymoma. Medical conditions that are associated with cancers are known as paraneoplastic syndromes, and up to 50% to 60% of patients with thymoma will have one of these related conditions. The most commonly associated condition with thymoma is myasthenia gravis, an autoimmune disease of the nerve-muscle junction that can manifest as weakness, fatigue, double vision, ptosis (drooping eyelid), and problems with swallowing.

Other associated conditions include other autoimmune diseases including pure red cell aplasia (underdevelopment of precursors for red blood cells in the bone marrow).

Medically Reviewed by a Doctor on 3/16/2016

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