General Information / Anatomy / Function / Statistics

• An unpaired organ located in the mediastinal cavity anterior to and above the heart
• Consists of two encapsulated lobes
• Lobes are divided into lobules consisting of a cortex and medulla
• Contains lymphoid tissue
• Important in the development of immune response in newborn
• Essential to the maturation of the thymic lymphoid cells called T cells which enter the circulation as lymphocytes
• Tumours may be encapsulated or invade adjacent structure
• Gross appearance is similar to thyroid gland
• Thymus cancers rarely spread outside the chest

Symptoms / Signs

• Often there are no symptoms
• Vague non-specific chest symptoms - cough, dyspnea (difficulty in breathing), dysphagia (difficulty in swallowing), chest tightness
• Advanced lesions may produce chest pain
• If the tumor is large, the neck and face may be swollen

 
Etiology / Carcinogens / Risks

• The cause is unknown
• Patients usually between 40 and 60 years
• Men and women affected equally
• Thymic abnormalities are frequent in patients with myasthenia gravis (muscle weakness)
• Rarely accompanied by immune disorders which include low red blood cell counts

Prevention

• No preventative measures known

Diagnosis / Screening / Staging / Grading / Types

• Biopsy is needed for a definite diagnosis
• 40% of tumours discovered on chest X-rays for unrelated reasons 
• Three major types:
  • Thymoma (most common)
  • Thymic carcinoma (uncommon)
  • Thymic carcinoid tumor (rare)

Staging

Treatment

Surgery

• Most effective treatment is complete removal (if possible)
• If tumour is encapsulated and can be removed with the thymus, most patients will be cured
• Recurrences take the form of pleural, pericardial or diaphragmatic implants

Radiotherapy

• Thymomas are relatively radiosensitive
• Radiotherapy may be helpful when given post-operatively for invasive thymoma

Chemotherapy

• Thymomas that are too advanced for surgical removal may be considered for pre-operative chemotherapy
• Chemotherapy may be considered for treatment of recurrent thymoma

Revised April 2000