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Thymoma - Cause, Signs, Symptoms, Diagnosis, Treatment and Complications

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Thymoma refers to a disease in which cancer cells form on the outer surface of the thymus. Read this article to know more about this disease.

Medically reviewed by

Dr. Kaushal Bhavsar

Published At April 21, 2022
Reviewed AtFebruary 21, 2023


The thymus is an organ located behind the sternum, and obtains its maximum weight at puberty and then it faces involution. Thymus helps in the development of cell-mediated immunity during the early stages of life. Thymoma is a tumor or neoplasm that develops with the cells of epithelium constituting the thymus.

It is known to be the most common tumor involving the front portion of the mediastinum and the prevalence ranges from 20 % - 25 % of all the tumors of the mediastinum and 50 % of masses involving the anterior location of the mediastinum. It shows a peak in incidence during the fourth and fifth decades of life and there is no sex predilection.

How Is It Caused?

The exact etiology has not been proven yet but it can be associated with certain syndromes like myasthenia gravis, dermatomyositis, systemic lupus erythematosus, Cushing syndrome, etc.

What Are the Signs and Symptoms of Thymoma?

Usually, the cases can be asymptomatic and it can be diagnosed during a routine examination or some other imaging studies being done to diagnose another case. However, at times it can show some symptoms that can depend on the size of the tumor. In that case, the following symptoms can be noticed:

1. Pain in the chest.

2. Difficulty in breathing or shortness of breath.

3. Cough.

Sometimes, the following symptoms may also occur but are less common in frequency:

1. Fever.

2. Loss of weight.

3. Sweating at night.

There have been cases wherein the tumor spreads to adjacent tissues like the heart, lungs, etc., and may cause symptoms associated with that particular region. Although children are known to have less prevalence than adults in developing thymoma, the symptoms are higher in children. The trachea or near trachea is the most common location for this tumor in children and thus, causing respiratory symptoms.

How Can It Be Diagnosed?

Initially, when you visit your physician, you will be asked certain questions about your past medical history and the symptoms you face at present. Following that, certain physical examinations will be done and then, testing for suspected syndromes may be done, if required and finally, imaging studies can be done. Some imaging studies that can be preferred are CT (computed tomography), radiography, positron emission tomography (PET), etc. Also, FNAC (fine needle aspiration cytology) can be done later to confirm the diagnosis.

What Are the Stages in Thymoma?

Thymoma can be staged using the Masaoka system. This is a very commonly used system for this tumor and includes stage I, II, III, and IV. Stage II and IV can be further divided into stages II a, II b, IV a, and IV b.

The Masaoka Staging System which is based on the anatomical extent of the lesion or tumor at the time of surgery is as follows:

  • I: Completely encapsulated.

  • IIA: Microscopic invasion through the capsule into surrounding fatty tissue.

  • IIB: Macroscopic invasion into the capsule.

  • III: Macroscopic invasion into adjacent organs.

  • IVA: Pleural or pericardial implants.

  • IVB: Lymphogenous or hematogenous metastasis to distant (extrathoracic) sites.

How Can It Be Treated?

The management can be either medical or surgical.

Medical Management

  • Chemotherapy

It is based on literature. Literature suggests that thymoma is sensitive to drugs, especially stage IV thymoma tumors.

  • Radiotherapy

This may also help in shrinking the tumor and it is beneficial to use as an adjunct or with the surgical method.

  • Corticosteroids

This is based on case reports. Case reports have shown that orally delivered corticosteroids have helped in the regression of tumors that are invasive in nature.

Multidisciplinary Approach

This type of approach can be used for tumors that cannot be resected. Based on certain studies or case reports, induction chemotherapy, surgical resection, postoperative radiation therapy, and consolidation chemotherapy can be preferred.

Options in the Future

Studies have proven biological and molecular changes in thymoma. Thus, a deeper understanding and evidence of such characteristics of tumors like specific tumor markers, etc., will help in establishing a better treatment plan.

Surgical Management

In most of the cases, the first line of treatment option for such tumors lies around surgical excision. This involves specific patient preparation, resection type, and also, the prognosis.

Are There Any Complications?

Yes, there have been reports of certain complications especially after the radiation therapy and sometimes, after surgical management. Some of the complications include radiation pericarditis, radiation pneumonitis, pulmonary fibrosis. The deaths have been reported in these tumors after or during treatment, and hence, the physician needs to assess and decide the proper treatment plan associated with radiation, chemotherapy, or surgery.

What Is the Prognosis?

The prognosis depends on various factors like the age of the patient, size of the tumor, the involvement of adjacent tissues, etc. The prognosis is known to be worse for symptomatic patients as they might have a malignant type of lymphoma. The most important factor to be considered before deciding the prognosis rate is the invasion of surrounding tissues by the tumor. Histologically, the features should be observed. The overall inspection of the tumor physically should also be done.

In other patients, there is a better prognosis after treatment and the survival rates have been documented to be around 10 years. The patients who have had thymectomy for the management of thymoma must be informed about the major side effects that can happen after the vaccination for yellow fever. The reason for the same has been attributed to the inadequate response of the T-cells to the live attenuated vaccine of yellow fever. In worst-case scenarios, even deaths have been reported.


Thymoma is a tumor involving the thymus gland and it can be benign or malignant. It has both better as well as poor prognosis depending on various factors. Early diagnosis can help in better management of the disease. Online medical platforms are proving to be a gift by helping patients to communicate with their physicians or specialists anywhere anytime. Consult your physician or specialist to get more details about this tumor.

Frequently Asked Questions


Is Thymoma a Serious Condition?

While many thymomas seem to act benignly and are noninvasive, the majority of thymomas have the potential to behave like cancer and spread outside of the thymus. Such an invasive thymoma is sometimes referred to as a malignant thymoma, and it can be serious.


Can Thymoma Cancer Be Cured?

Adults can typically have all or part of their thymus removed without any complications. Thymomas also have a tendency to grow slowly and, if at all, only spread locally. These factors make the majority of thymomas curable. The total removal of the thymus gland is the most common procedure for thymus tumors (including any tumor). It is known as a thymectomy. Thymectomy is suggested when cells in the thymus turn cancerous (thymoma). 


Who Is at an Increased Risk of Developing Thymoma?

There are not any well-established hereditary, environmental, or behavioral risk factors for a thymoma or thymic cancer. Age and ethnicity are the only factors known to increase risk. Thymomas typically affect people between the ages of 30 and 70 (with a median age of 50), while they incredibly rarely affect children as well. Blacks and Asians/Pacific Islanders have a higher incidence of thymoma than whites, which may be due to genetic risk factors.


Is It Possible to Remove a Thymoma?

The total removal of the thymus gland is the most common procedure for thymus tumors (including any tumor). It is known as a thymectomy. Thymectomy is suggested when cells in the thymus turn cancerous (thymoma). Patients with stage III and IVa thymoma are given chemotherapy before surgery, and these patients may receive radiation therapy following surgery.


Is Thymoma a Cancerous Condition?

Both thymoma and thymic carcinoma are conditions in which the thymus develops malignant (cancer) cells. Thymic epithelial tumors, also known as thymoma and thymic carcinoma, are two uncommon malignancies that can develop in the cells that line the outside of the thymus. Thymectomy (total removal of the thymus gland) is suggested when cells in the thymus turn cancerous (thymoma).


Are a Majority of Thymomas Cancerous?

Thymomas and thymic carcinomas are malignant (cancerous) conditions that develop in the thymus. Thymoma is usually associated with myasthenia gravis (a condition in which muscles under voluntary control get tired quickly and feel weak). About one in 10 thymic tumors are found to be thymic carcinoma. Non-cancerous tumors of the thymus are uncommon (rare). 


How Long Is Chemo Required for Thymoma?

Chemotherapy drugs are used to kill cancerous cells if the tumor cannot be removed through surgical procedures. Typically, chemotherapy treatments for thymoma last for three to four weeks, and treatment encompasses four to six cycles. Chemotherapy may be suggested before surgery to shrink the tumors or to treat recurrence. However, surgery is the preferred mode of treatment for treating thymomas. 


What Is Meant by Early-Stage Thymoma?

Thymomas in the early stages are uncommon, slow-growing tumors of the thymus gland. Early-stage thymomas are rare, idle tumors of the thymus gland. Thymomas can appear at any age, but they are prevalent between the ages of 35 and 70. When compared to thymic carcinoma, thymomas are less serious.


Does Thymoma Grow Fast?

Thymoma develops gradually and rarely spreads beyond the thymus. Type A thymomas tend to grow slowly, while type B thymomas can grow rapidly. Thymomas tend to grow slowly when compared to thymic carcinomas, which grow quickly and spread. According to the American Society of Clinical Oncology, about 400 people are diagnosed with thymomas every year. 


How Can Thymoma Be Diagnosed?

Thymoma can be diagnosed in the following ways:
- Chest X-ray- This enables us to determine how defined the edges of the tumors are.
- CT (Computed Tomography) Scan- Usually, this is the only diagnostic imaging technique that is sufficient to identify thymoma or thymic carcinoma.
- MRI (Magnetic Resonance Imaging) Scan- This scan provides a detailed image of the tumor.
- PET (Positron Emission Tomography) Scan or a PET/CT Scan- Through injection of a safe, radioactive sugar into the veins, the contrast medium accumulates around cancer cells, thereby enabling the physician to diagnose the presence of a tumor.
- Biopsy- In this method, tumor cells are removed and examined under a microscope. 


Is Surgery for Thymoma Painful?

A thymectomy is a surgery that is done to remove the thymus gland. Surgeons incorporate open or minimally invasive techniques for a thymectomy. Pain following the surgery is minimal and temporary, and it gradually resolves within two to five days. The recovery rate is usually quick. However, in patients with myasthenia gravis, it might take a year or more to expect the results.


How Can a Thymoma Be Removed?

Surgical complete resection is the most preferred treatment option for thymoma. In the surgical procedure, the lymph nodes and the thymus or lung lining are removed if the cancer cells spread to that region. If it is not possible to remove the tumor entirely and safely, then as much as cancerous tissues that can be removed are is done. Other treatment methods include radiation, chemotherapy, targeted therapy, and immunotherapy. 


Can Stress Result in the Development of Thymoma?

The thymus is frequently referred to as the body's ‘barometer of stress’  because it is vulnerable to acute stress-induced atrophy. Stress can result in a condition called acute thymic atrophy, which can affect the functioning of the immune system. A notable response of the thymus to stress is a reduction in double-positive thymocytes and decreased output of T-cells to the periphery, which can result in a reduction in the size of the thymus gland.
Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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