OVERVIEW

What is thymoma?

Thymoma is a type of mediastinal tumor originating from thymic components ^[1].

Based on its nature, thymomas are mainly classified as benign or malignant (including invasive thymomas and thymic carcinomas), with significant differences in treatment and prognosis ^[2]. Since many benign thymomas still metastasize or recur after surgery, they are generally treated as malignant tumors during initial evaluation ^[3].

Thymomas have few specific symptoms, which are often atypical and mostly accompany other conditions. These accompanying symptoms are numerous and complex, such as chest tightness and pain, making diagnosis challenging. Most cases are detected during physical examinations or after symptoms appear. Some patients are already inoperable at diagnosis, resulting in poor prognosis ^[2,3].

How is thymoma classified?

1. Based on pathological features, thymomas can be divided into ^[4]:

   1. Type A, AB, B1, B2, and B3 thymomas: These types generally have a favorable prognosis, with a 5-year survival rate as high as 90%, meaning about 90 out of 100 patients survive for 5 years or longer.
   2. Thymic carcinoma: Prognosis is poorer, with a 5-year survival rate of about 55%.

2. Based on tumor morphology, thymomas can be classified as ^[1]:

   1. Non-invasive thymoma: Although it may adhere to adjacent organs, it has a complete capsule with minimal adhesion. The tumor is mobile and easily resectable, leading to a high survival rate after radical resection.
   2. Invasive thymoma: Pathological examination may show benign features, but the tumor lacks clear boundaries with surrounding tissues and can invade nearby structures. Even with benign features, it is closely associated with adjacent tissues, has poor mobility, and a higher risk of metastasis.

Is thymoma common?

Thymoma is a rare disease with low incidence ^[5]. According to the 2019 China Cancer Registry Annual Report, the incidence of thymoma in China in 2016 was 4.09 per million, meaning about 4 people per million were diagnosed with thymoma ^[6].

The disease predominantly affects individuals aged 50–60, with equal gender distribution, and is rare in children and adolescents [7].

SYMPTOMS

What are the symptoms of thymoma?

Thymoma usually has no symptoms in its early stages. However, as the tumor grows larger and compresses or invades other organs in the mediastinum or affects nerve function, related clinical symptoms may appear ^[1,2].

1. Neurological symptoms: Symptoms vary depending on the affected nerves.
   1. Sympathetic nerve: Drooping eyelid, constricted pupil, and sunken eyeball on the same side.
   2. Recurrent laryngeal nerve: Hoarseness.
   3. Phrenic nerve: Difficulty breathing.
2. Respiratory symptoms: The most common include coughing (sudden, frequent episodes) and wheezing (a high-pitched whistling sound during breathing). Difficulty breathing may also occur, manifesting as cyanosis (bluish skin) and rapid breathing, sometimes accompanied by wheezing.
3. Cardiovascular symptoms: Compression of the superior vena cava may lead to jugular vein distension and edema in the upper chest. Compression of the heart can cause chest tightness, palpitations, or arrhythmia (irregular heartbeat).
4. About 1/3 of thymoma patients may develop myasthenia gravis, presenting as drooping eyelids and muscle weakness ^[1,2].

What are the complications of thymoma?

1. Pernicious anemia: Some thymoma patients may develop pernicious anemia, characterized by pale skin, fatigue, and lethargy.
2. Cachexia: Primarily associated with malignant thymoma. When tumor cells metabolize abnormally fast, they absorb the patient's nutrients, leading to malnutrition (cachexia). Symptoms include weight loss, fatigue, and emaciation.

CAUSES

What are the causes of thymoma?

The exact cause of thymoma is unclear, but it may be related to the following factors ^[1].

1. Radiation: Radiation can cause genetic mutations in normal thymic tissue cells or lead to disordered repair when the thymus is damaged, ultimately triggering tumor formation.
2. EBV infection: EBV, or Epstein-Barr virus, belongs to the herpesvirus family. Studies suggest EBV infection is a high-risk factor for thymoma, though the exact mechanism remains unknown.

Is thymoma contagious?

This disease is not contagious.

Is thymoma hereditary?

There is no evidence to confirm that thymoma is hereditary ^[1].

DIAGNOSIS

What tests are needed for thymoma?

1. CT scan: Doctors use CT scans to determine the location, size, and adhesion of the thymoma to surrounding tissues, helping to preliminarily assess its severity.
2. MRI (Magnetic Resonance Imaging): More accurate than CT in evaluating cystic masses and tumor infiltration into surrounding fat.
3. Histopathological examination: For larger thymomas, a CT-guided percutaneous tumor biopsy may be performed before surgery, which is the gold standard for diagnosis ^[2].
4. Blood test: Determines whether anemia is present and assesses its severity.
5. Chest X-ray: Helps locate the tumor and determine its shape and size. Both frontal and lateral images are usually required.
6. Electrocardiogram (ECG): Evaluates heart function and checks whether the tumor affects the heart.

Which diseases can thymoma be easily confused with?

As thymoma is a type of mediastinal tumor and relatively rare, its symptoms are similar to other anterior mediastinal tumors (e.g., lymphoma, teratoma). Doctors often rely on imaging tests to thoroughly examine the thymus and determine whether the tumor is a thymoma or another mediastinal tumor based on its location.

TREATMENT

Which department should I visit for thymoma?

Thoracic surgery, medical oncology, radiation oncology.

How is thymoma treated?

1. Surgical treatment

   1. Complete surgical resection remains the primary and most effective treatment for thymoma and is the most important predictor of long-term survival ^[1].
   2. Indications: Patients in generally good condition who can tolerate surgery (e.g., no significant impairment of heart, lung, or other organ functions) and whose thymoma has not spread extensively (e.g., no extra-thoracic metastasis) or metastasized distantly (e.g., no intracranial metastasis). A consultation with a specialist is necessary.
   3. Surgical approach: This depends on the tumor's characteristics and its invasion of surrounding tissues, and will be customized by highly specialized surgeons.

2. Radiation therapy
   Thymomas are generally sensitive to radiotherapy, which plays a significant role in treatment, including the following ^[3].

   3. Preoperative radiotherapy: Suitable for patients with large, deep-seated, rapidly growing, highly malignant tumors or those ineligible for direct surgery.
   4. Postoperative adjuvant radiotherapy: Aims to enhance local control and prevent recurrence or metastasis.

   Note: Radiotherapy may cause adverse effects. With appropriate and lower doses, side effects are minimal, but higher doses may lead to complications such as anemia, thrombocytopenia, immune suppression, and fever.

3. Chemotherapy
   Thymomas are also sensitive to chemotherapy ^[3].

   4. Indications: Patients with unresectable or incompletely resectable advanced tumors, high recurrence risk, or recurrent cases.
   5. Common combination chemotherapy drugs: Cyclophosphamide, doxorubicin, cisplatin, vincristine, etoposide, ifosfamide, epirubicin, etc.
   6. Adverse effects: May include thromboembolism, infections, gangrene, delayed wound healing, etc.

4. Symptomatic treatment

   1. For patients with significant myasthenia gravis symptoms, anticholinesterase inhibitors (e.g., pyridostigmine) may be used ^[1]. High doses may cause nausea, vomiting, or excessive salivation. Use cautiously in asthma patients and avoid in those with urinary obstruction.
   2. Severe pernicious anemia may require blood transfusions.

DIET & LIFESTYLE

What should be paid attention to in the diet for thymoma?

1. Balanced diet: Maintain a reasonable diet, consume foods high in protein and vitamins but low in fat, such as pure milk, fresh eggs, lean meat, etc., to ensure adequate nutrition and avoid malnutrition to some extent.
2. Eat smaller, more frequent meals, chew food slowly, and avoid eating quickly or in large bites. Avoid overeating to prevent increasing the burden on the stomach and mediastinum, which may hinder recovery.
3. Increase intake of foods that boost immunity (such as apricots, sea cucumbers, bird's nest, etc.) to enhance the body's ability to fight the disease and aid in recovery.
4. Avoid spicy and stimulating foods like chili peppers, Sichuan peppercorns, and other spices. Avoid strong tea, coffee, and energy drinks, as these may interfere with the body's recovery.

What should thymoma patients pay attention to in daily life?

1. Ensure adequate sleep: Maintain a regular sleep schedule with sufficient rest (generally 7-8 hours for adults, waking up feeling refreshed). Develop good sleep habits, as quality sleep aids in physical recovery and mental relaxation.
2. Engage in reasonable and scientific exercise: Thymoma patients may experience symptoms like myasthenia gravis. Avoiding exercise entirely can lead to muscle atrophy over time. Patients who can move around should engage in gentle activities like walking in a safe environment under the supervision of medical staff or family members to promote muscle growth, prevent atrophy, and improve stamina. Bedridden patients can receive limb massages (e.g., gentle kneading) from caregivers to stimulate muscle nerves.
3. Psychological care: Patients may experience anxiety, depression, or other psychological issues due to discomfort or fear of malignancy. Family members should create a warm and supportive environment, offering care and encouragement to the patient.

Is follow-up necessary for thymoma?

Yes.

1. For patients with benign thymoma, the frequency and timing of follow-ups should follow the doctor's instructions.
2. Patients diagnosed with malignant thymoma should undergo lifelong follow-up. After surgery, they should be re-examined at least every 3 months for the first 2 years, then every 6 months, and annually after 5 years. Follow-ups help detect signs of recurrence or metastasis early ^[1].

PREVENTION

Can thymoma be prevented?

Thymoma is a rare disease with an unclear pathogenesis, so there are no effective preventive measures. However, for the general population, maintaining a healthy lifestyle can reduce the risk of disease:

1. Maintain a positive mood: Keep a good mindset and avoid emotional stress and fluctuations.
2. Strengthen nutrition: Eat a balanced diet with various nutrients such as protein and dietary fiber (e.g., milk, fish, eggs, millet, wheat, etc.). Consume fresh fruits (e.g., apples) and opt for light, easily digestible meals.
3. Exercise moderately: Engage in appropriate and timely physical activity (at least 5 days a week, 30 minutes daily) to improve mental well-being, regulate bodily functions, and enhance immunity ^[8].
4. Schedule regular check-ups: Undergo medical examinations every six months to a year.

Can thymoma recur?

Yes. Recurrence is common in malignant thymomas, with local recurrence being more frequent than distant metastasis. Local recurrence refers to the reappearance of tumor cells in the thymus or nearby tissues, such as the pleura, lungs, or mediastinum. Distant metastasis occurs when tumor cells spread to organs farther from the thymus or mediastinum, such as the liver or bones ^[1].

Studies show that the average recurrence time for thymoma is 5 years, with the longest intervals being 10–20 years. Therefore, thymoma patients should undergo follow-up monitoring for at least 20 years ^[1].

How to prevent thymoma recurrence?

During thymoma surgical resection, the tumor should be removed as thoroughly as possible. The more completely the tumor is excised, the lower the likelihood of recurrence and the longer the survival time ^[7].

Additionally, post-surgical treatments such as radiotherapy or chemotherapy should be administered as prescribed to effectively curb the spread of cancer cells.

Lastly, maintaining a healthy and active lifestyle is also one of the effective measures.