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Thymoma

Updated : February 23, 2024





Background

Thymoma is a kind of tumor that is comparatively uncommon and arises from the thymus gland’s epithelial cells. The thymus is a small organ situated in the upper chest, directly in front of the heart and behind the breastbone.

It plays a crucial role in the development and maturation of a specific type of white blood cell called T-lymphocytes, which are vital for a healthy immune system. 

Thymomas are generally slow-growing tumors that tend to remain localized within the thymus. However, their behavior can vary significantly and may sometimes be associated with other medical conditions, such as myasthenia gravis or other autoimmune disorders.

Epidemiology

Incidence and Prevalence: Thymic carcinomas & thymomas represent the prevalent masses found in the anterior mediastinum, comprising around 20% of all neoplasms located in this area. Most people are diagnosed in their fourth or sixth decade of life; these conditions do not display any specific inclination towards a particular gender or racial group. 

Association with Other Conditions: Thymomas are often associated with other medical conditions, such as myasthenia gravis, an autoimmune neuromuscular disorder. Between percent and 50 percent of those with thymoma also have myasthenia gravis.  

Risk Factors: The exact causes of thymomas are not well understood, and specific risk factors for developing thymomas have not been definitively identified. However, some studies suggest that genetic factors, certain infections, and exposure to radiation might play a role in the development of thymomas. 

 

Anatomy

Pathophysiology

Abnormal cellular growth: Thymomas originate from epithelial cells within the thymus. These cells proliferate uncontrollably, leading to the formation of a tumor. The mechanisms triggering this abnormal growth are not completely clear, but genetic mutations and alterations in signaling pathways likely contribute. 

Disruption of normal thymus function: As the thymoma grows, it displaces and compresses the normal thymic tissue. This can disrupt the regular functioning of the thymus, impacting its role in the maturation and differentiation of T-cells. The altered microenvironment within the thymus due to the presence of the tumor can affect the normal processes of T-cell development. 

Autoimmune associations: The relationship between thymoma and autoimmunity is not fully understood, but it’s believed that the abnormal T-cell development or the production of autoantibodies within the tumor microenvironment may contribute to the development of autoimmune conditions. 

Potential metastasis: Thymomas typically grow slowly and tend to remain localized within the thymus. However, in some cases, they can invade nearby structures or metastasize to distant sites, although metastasis is less common compared to other cancers. 

Immune system implications: The thymus is involved in educating T-cells and regulating the immune response. The presence of a thymoma may alter the immune system’s function, potentially leading to immune system dysfunction or dysregulation. This disruption can manifest as an increased susceptibility to infections or the development of autoimmune conditions. 

Etiology

Autoimmune Diseases: Thymoma is commonly associated with autoimmune disorders, particularly myasthenia gravis, wherein the immune system attacks the body’s own tissues, leading to muscle weakness and fatigue. About 30% to 50% of patients with thymoma have myasthenia gravis. 

Age and Gender: Thymomas can occur at any age but are more commonly diagnosed in individuals between 40 and 60 years old. There might be a slight predilection for men in some studies. 

Radiation Exposure: Some research suggests a possible link between radiation exposure and the development of thymoma, but the evidence supporting this association is limited. 

Other Factors: Environmental factors or exposures to certain chemicals might play a role, although specific causative agents have not been identified. 

Genetics

Prognostic Factors

Tumor stage: The stage of the thymoma, determined by the size of the tumor and if it has extended to organs or tissues close, is a crucial prognostic factor. Staging helps predict the prognosis and guides treatment decisions. 

Histological subtype: Thymomas can be classified into different histological subtypes based on their appearance under the microscope. Certain subtypes, such as type A or AB thymomas, tend to have a better prognosis compared to more aggressive subtypes like type C thymomas. 

Tumor invasiveness: The invasiveness of the tumor, whether it has invaded nearby structures or metastasized to distant sites, significantly impacts the prognosis. Tumors that are confined to the thymus without invasion into surrounding tissues generally have a better prognosis. 

Tumor resectability: The extent to which the tumor can be surgically removed (resected) plays a critical role in determining the prognosis. Complete resection of the tumor with clear margins often results in better outcomes compared to cases where complete removal is challenging. 

 

Clinical History

  • Age group 

Thymoma, a type of tumor that forms in the thymus gland, can occur at any age. However, it most commonly affects individuals between the ages of 40 and 60 years old. Although it is uncommon in children and teens, it can happen to anyone at any age. 

 

Physical Examination

General Examination: 

Evaluation of overall appearance, including signs of weight loss, fatigue, or generalized weakness. 

Respiratory Examination: 

Auscultation of the lungs for abnormal breath sounds such as diminished breath sounds, crackles, or wheezing. 

Examination for any signs of difficulty in breathing or shortness of breath. 

Chest Examination: 

Inspection of the chest for any visible abnormalities or asymmetry. 

Palpation of the chest wall to identify masses, tenderness, or enlarged lymph nodes. 

Neurological Examination: 

Assessment for any neurological deficits that might be associated with advanced disease, such as weakness or sensory changes in the limbs. 

Cardiovascular Examination: 

Examination of the heart for murmurs, irregular heartbeats, or signs of fluid buildup (e.g., edema). 

 

Age group

Associated comorbidity

Myasthenia Gravis (MG): This is the most associated autoimmune condition with thymoma. Around 30-50% of individuals diagnosed with thymoma also have myasthenia gravis. Removal of the thymoma can sometimes improve the symptoms of myasthenia gravis. 

Other Autoimmune Disorders: Besides myasthenia gravis, thymoma can also be associated with other autoimmune conditions such as pure red cell aplasia, systemic lupus erythematosus, rheumatoid arthritis, and others. 

Hematological Conditions: There are associations between thymoma and certain blood disorders like aplastic anemia, this has an affect on the bone marrow’s ability to produce blood cells. 

Endocrine Disorders: Thymoma can rarely be linked with endocrine disorders like Cushing’s syndrome, which involves an excess of cortisol hormone production. 

Immunodeficiency Syndromes: Thymoma may also be associated with certain immunodeficiency syndromes due to abnormalities in the immune system caused by the tumor. 

Smoking: While not a direct comorbidity, there have been studies suggesting an association between thymoma and smoking. However, more research is needed to establish a definitive causal link. 

Radiation Exposure: In some cases, prior radiation exposure to the chest area has been suggested as a potential risk factor for the development of thymoma. 

Associated activity

Acuity of presentation

Asymptomatic Discovery: Thymomas are sometimes discovered incidentally during imaging studies performed for unrelated reasons. In such cases, there might be no symptoms present. 

Gradual Onset of Symptoms: Thymomas can cause non-specific symptoms that develop slowly over time. These symptoms might include chest pain, cough, shortness of breath, fatigue, and weakness. 

Compression Symptoms: Larger thymomas can compress nearby structures such as the airways, blood vessels, or nerves in the chest. This can result in more acute symptoms such as difficulty breathing, cough, chest pain, superior vena cava syndrome, or hoarseness if the tumor affects the recurrent laryngeal nerve. 

Paraneoplastic Syndromes: Thymomas are associated with paraneoplastic syndromes, where the tumor secretes substances that affect other parts of the body. These syndromes can cause symptoms such as myasthenia gravis, pure red cell aplasia, hypogammaglobulinemia, and others. These manifestations may present acutely or develop gradually. 

Neurological Symptoms: The occurrence of neurological symptoms like weakness, sensory alterations, or neurological impairments can arise from the compression of the spinal cord or nerves, contingent upon the tumor’s location and size. 

 

Differential Diagnoses

Metastatic tumors: Tumors originating from distant sites and metastasizing to the mediastinum, such as lung cancer, breast cancer, or renal cell carcinoma, can resemble thymoma. 

Neurogenic tumors: Tumors arising from nerve tissues, such as neurofibroma, schwannoma, or neuroblastoma, may occur in the mediastinum and mimic thymoma. 

Sarcoidosis: Granulomatous inflammation can involve the mediastinal lymph nodes, leading to mediastinal lymphadenopathy. 

Lymphoma: Both Hodgkin’s and non-Hodgkin’s lymphomas can occur in the mediastinum and may resemble thymoma in imaging studies. 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Surgery: The main course of treatment for thymomas is oftenly surgery. The aim is to remove the tumour as much as possible while trying to keep as much good tissue intact. The extent of surgery can vary from a complete thymectomy to a more limited resection, depending on the stage and location of the tumor. 

Radiation Therapy: Surgery can be performed either before or after radiation therapy, especially if the tumor is unresectable or if there’s a high risk of recurrence. It can also be used as the primary treatment for inoperable cases or as adjuvant therapy to destroy any remaining cancer cells post-surgery. 

Chemotherapy: In some cases, chemotherapy may be recommended, particularly for more advanced or metastatic thymomas. Chemotherapy drugs like cisplatin, doxorubicin, vincristine, and cyclophosphamide are commonly used either alone or in combination. 

Targeted Therapy and Immunotherapy: Targeted therapies and immunotherapies are areas of ongoing research in the treatment of thymomas.  

Follow-up Care: Regular follow-up care is crucial after treatment for thymoma. This involves routine check-ups, imaging tests, and blood tests to check for metastasis or recurrence signals. Additionally, managing any treatment-related side effects and providing support for the patient’s overall well-being is an integral part of post-treatment care. 

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Lifestyle modifications in treating thymoma

Smoking Cessation: There is evidence that smoking increases the risk of thymomas. As a result, giving up smoking is essential since it can greatly lower the chance of getting malignant tumours.

Furthermore, as secondhand smoke can affect immunological function and general health, it is equally crucial for people with thymoma to avoid it. 

Healthy Diet and Lifestyle: A well-balanced diet can support overall health and may aid in bolstering the immune system’s function.  

Reducing Environmental Toxins: Minimizing exposure to environmental toxins and pollutants whenever possible can be beneficial. This includes avoiding exposure to chemicals, pollutants, and other harmful substances that could potentially affect the immune system or aggravate existing health conditions. 

Stress Management: Participating in stress-relieving practices like meditation, yoga, mindfulness, or accessing counseling or support groups can offer advantages to individuals diagnosed with thymoma. 

Compliance with Medical Recommendations: Following medical advice, adhering to prescribed treatments, attending regular check-ups, and monitoring for any potential recurrence or complications are essential components in managing thymoma. Compliance with medications and therapies as prescribed by healthcare professionals is crucial. 

Role of corticosteroids in treating thymoma

Corticosteroids 

Case studies have shown that oral glucocorticoid therapy can cause an invasive thymoma to recede. In one instance, the patient’s thymoma and related symptoms completely disappeared, and after a year, there was no radiologic recurrence. 

Role of multidisciplinary approach in treating thymoma

Multidisciplinary approach 

octreotide 0.5 mg subcutaneously every eight hours used alone or in combination with prednisone 0.6 mg/kg a day was assessed in 38 individuals who had somatostatin receptor-expressing advanced thymomas. 

Out of the total 38 individuals, four patients representing 10.5% exhibited a partial response solely with the administration of octreotide.

Meanwhile, among the subset of 21 patients who were treated with a combination of prednisone & octreotide, two experienced complete responses, while an additional four patients showed partial responses. 

Role of surgery in treating thymoma

Intervention with procedure 

Surgery is typically the primary treatment for thymomas that have not spread beyond the thymus. The primary objective during surgery is to extract the maximum amount of the tumor while safeguarding the neighboring healthy tissue.

The specific surgical procedure undertaken is determined by several factors, including the tumor’s size and its location within the body. 

Thymectomy: This surgical procedure involves the removal of the thymus gland, where the tumor originates. It can be done through different techniques, including open surgery (sternotomy) or minimally invasive approaches such as video-assisted thoracoscopic surgery or robotic-assisted surgery.  

Lymph node removal: If there’s a chance the cancer has spread, adjacent lymph nodes could occasionally also be removed during surgery. 

Role of management in treating thymoma

Phases of Management: 

Diagnosis: 

Clinical evaluation: This involves a thorough medical history review and physical examination. 

Imaging studies: Chest X-rays, CT scans, MRI, and PET scans help in identifying the size, location, and extent of the tumor. 

Biopsy: Through a biopsy, a tissue sample is collected in order to confirm the diagnosis and identify the type and stage of the tumour. 

Staging: 

Determining the stage of thymoma involves assessing the tumor size, invasion into nearby tissues, and spread to distant organs. Staging helps in planning the appropriate treatment strategy. 

Treatment: 

Surgery: Surgical removal of the thymoma (thymectomy) is the primary treatment for localized tumors. It may involve minimally invasive techniques or open surgery. 

Chemotherapy: Depending on the stage and characteristics of the thymoma, chemotherapy may be recommended before or after surgery to shrink the tumor or target remaining cancer cells. 

Radiation therapy: Radiation therapy may be done either prior to or following surgery in certain instances in order to eradicate cancer cells or lower the chance of recurrence. 

Follow-up and Monitoring: 

To tracking the patient’s progress, managing any possible adverse effects of therapy, and checking signs for any indications of recurrence, follow-up appointments with medical professionals are crucial. 

Imaging tests and other diagnostic procedures may be performed periodically to assess the response to treatment and detect any recurrence. 

Supportive Care: 

Supportive care focuses on managing symptoms, providing psychological support, and attending to the patient’s general health both during and after therapy. 

Palliative care may be introduced to improve the quality of life for patients with advanced thymoma or those who cannot undergo curative treatment. 

Medication

Media Gallary

Thymoma

Updated : February 23, 2024




Thymoma is a kind of tumor that is comparatively uncommon and arises from the thymus gland’s epithelial cells. The thymus is a small organ situated in the upper chest, directly in front of the heart and behind the breastbone.

It plays a crucial role in the development and maturation of a specific type of white blood cell called T-lymphocytes, which are vital for a healthy immune system. 

Thymomas are generally slow-growing tumors that tend to remain localized within the thymus. However, their behavior can vary significantly and may sometimes be associated with other medical conditions, such as myasthenia gravis or other autoimmune disorders.

Incidence and Prevalence: Thymic carcinomas & thymomas represent the prevalent masses found in the anterior mediastinum, comprising around 20% of all neoplasms located in this area. Most people are diagnosed in their fourth or sixth decade of life; these conditions do not display any specific inclination towards a particular gender or racial group. 

Association with Other Conditions: Thymomas are often associated with other medical conditions, such as myasthenia gravis, an autoimmune neuromuscular disorder. Between percent and 50 percent of those with thymoma also have myasthenia gravis.  

Risk Factors: The exact causes of thymomas are not well understood, and specific risk factors for developing thymomas have not been definitively identified. However, some studies suggest that genetic factors, certain infections, and exposure to radiation might play a role in the development of thymomas. 

 

Abnormal cellular growth: Thymomas originate from epithelial cells within the thymus. These cells proliferate uncontrollably, leading to the formation of a tumor. The mechanisms triggering this abnormal growth are not completely clear, but genetic mutations and alterations in signaling pathways likely contribute. 

Disruption of normal thymus function: As the thymoma grows, it displaces and compresses the normal thymic tissue. This can disrupt the regular functioning of the thymus, impacting its role in the maturation and differentiation of T-cells. The altered microenvironment within the thymus due to the presence of the tumor can affect the normal processes of T-cell development. 

Autoimmune associations: The relationship between thymoma and autoimmunity is not fully understood, but it’s believed that the abnormal T-cell development or the production of autoantibodies within the tumor microenvironment may contribute to the development of autoimmune conditions. 

Potential metastasis: Thymomas typically grow slowly and tend to remain localized within the thymus. However, in some cases, they can invade nearby structures or metastasize to distant sites, although metastasis is less common compared to other cancers. 

Immune system implications: The thymus is involved in educating T-cells and regulating the immune response. The presence of a thymoma may alter the immune system’s function, potentially leading to immune system dysfunction or dysregulation. This disruption can manifest as an increased susceptibility to infections or the development of autoimmune conditions. 

Autoimmune Diseases: Thymoma is commonly associated with autoimmune disorders, particularly myasthenia gravis, wherein the immune system attacks the body’s own tissues, leading to muscle weakness and fatigue. About 30% to 50% of patients with thymoma have myasthenia gravis. 

Age and Gender: Thymomas can occur at any age but are more commonly diagnosed in individuals between 40 and 60 years old. There might be a slight predilection for men in some studies. 

Radiation Exposure: Some research suggests a possible link between radiation exposure and the development of thymoma, but the evidence supporting this association is limited. 

Other Factors: Environmental factors or exposures to certain chemicals might play a role, although specific causative agents have not been identified. 

Tumor stage: The stage of the thymoma, determined by the size of the tumor and if it has extended to organs or tissues close, is a crucial prognostic factor. Staging helps predict the prognosis and guides treatment decisions. 

Histological subtype: Thymomas can be classified into different histological subtypes based on their appearance under the microscope. Certain subtypes, such as type A or AB thymomas, tend to have a better prognosis compared to more aggressive subtypes like type C thymomas. 

Tumor invasiveness: The invasiveness of the tumor, whether it has invaded nearby structures or metastasized to distant sites, significantly impacts the prognosis. Tumors that are confined to the thymus without invasion into surrounding tissues generally have a better prognosis. 

Tumor resectability: The extent to which the tumor can be surgically removed (resected) plays a critical role in determining the prognosis. Complete resection of the tumor with clear margins often results in better outcomes compared to cases where complete removal is challenging. 

 

  • Age group 

Thymoma, a type of tumor that forms in the thymus gland, can occur at any age. However, it most commonly affects individuals between the ages of 40 and 60 years old. Although it is uncommon in children and teens, it can happen to anyone at any age. 

 

General Examination: 

Evaluation of overall appearance, including signs of weight loss, fatigue, or generalized weakness. 

Respiratory Examination: 

Auscultation of the lungs for abnormal breath sounds such as diminished breath sounds, crackles, or wheezing. 

Examination for any signs of difficulty in breathing or shortness of breath. 

Chest Examination: 

Inspection of the chest for any visible abnormalities or asymmetry. 

Palpation of the chest wall to identify masses, tenderness, or enlarged lymph nodes. 

Neurological Examination: 

Assessment for any neurological deficits that might be associated with advanced disease, such as weakness or sensory changes in the limbs. 

Cardiovascular Examination: 

Examination of the heart for murmurs, irregular heartbeats, or signs of fluid buildup (e.g., edema). 

 

Myasthenia Gravis (MG): This is the most associated autoimmune condition with thymoma. Around 30-50% of individuals diagnosed with thymoma also have myasthenia gravis. Removal of the thymoma can sometimes improve the symptoms of myasthenia gravis. 

Other Autoimmune Disorders: Besides myasthenia gravis, thymoma can also be associated with other autoimmune conditions such as pure red cell aplasia, systemic lupus erythematosus, rheumatoid arthritis, and others. 

Hematological Conditions: There are associations between thymoma and certain blood disorders like aplastic anemia, this has an affect on the bone marrow’s ability to produce blood cells. 

Endocrine Disorders: Thymoma can rarely be linked with endocrine disorders like Cushing’s syndrome, which involves an excess of cortisol hormone production. 

Immunodeficiency Syndromes: Thymoma may also be associated with certain immunodeficiency syndromes due to abnormalities in the immune system caused by the tumor. 

Smoking: While not a direct comorbidity, there have been studies suggesting an association between thymoma and smoking. However, more research is needed to establish a definitive causal link. 

Radiation Exposure: In some cases, prior radiation exposure to the chest area has been suggested as a potential risk factor for the development of thymoma. 

Asymptomatic Discovery: Thymomas are sometimes discovered incidentally during imaging studies performed for unrelated reasons. In such cases, there might be no symptoms present. 

Gradual Onset of Symptoms: Thymomas can cause non-specific symptoms that develop slowly over time. These symptoms might include chest pain, cough, shortness of breath, fatigue, and weakness. 

Compression Symptoms: Larger thymomas can compress nearby structures such as the airways, blood vessels, or nerves in the chest. This can result in more acute symptoms such as difficulty breathing, cough, chest pain, superior vena cava syndrome, or hoarseness if the tumor affects the recurrent laryngeal nerve. 

Paraneoplastic Syndromes: Thymomas are associated with paraneoplastic syndromes, where the tumor secretes substances that affect other parts of the body. These syndromes can cause symptoms such as myasthenia gravis, pure red cell aplasia, hypogammaglobulinemia, and others. These manifestations may present acutely or develop gradually. 

Neurological Symptoms: The occurrence of neurological symptoms like weakness, sensory alterations, or neurological impairments can arise from the compression of the spinal cord or nerves, contingent upon the tumor’s location and size. 

 

Metastatic tumors: Tumors originating from distant sites and metastasizing to the mediastinum, such as lung cancer, breast cancer, or renal cell carcinoma, can resemble thymoma. 

Neurogenic tumors: Tumors arising from nerve tissues, such as neurofibroma, schwannoma, or neuroblastoma, may occur in the mediastinum and mimic thymoma. 

Sarcoidosis: Granulomatous inflammation can involve the mediastinal lymph nodes, leading to mediastinal lymphadenopathy. 

Lymphoma: Both Hodgkin’s and non-Hodgkin’s lymphomas can occur in the mediastinum and may resemble thymoma in imaging studies. 

Surgery: The main course of treatment for thymomas is oftenly surgery. The aim is to remove the tumour as much as possible while trying to keep as much good tissue intact. The extent of surgery can vary from a complete thymectomy to a more limited resection, depending on the stage and location of the tumor. 

Radiation Therapy: Surgery can be performed either before or after radiation therapy, especially if the tumor is unresectable or if there’s a high risk of recurrence. It can also be used as the primary treatment for inoperable cases or as adjuvant therapy to destroy any remaining cancer cells post-surgery. 

Chemotherapy: In some cases, chemotherapy may be recommended, particularly for more advanced or metastatic thymomas. Chemotherapy drugs like cisplatin, doxorubicin, vincristine, and cyclophosphamide are commonly used either alone or in combination. 

Targeted Therapy and Immunotherapy: Targeted therapies and immunotherapies are areas of ongoing research in the treatment of thymomas.  

Follow-up Care: Regular follow-up care is crucial after treatment for thymoma. This involves routine check-ups, imaging tests, and blood tests to check for metastasis or recurrence signals. Additionally, managing any treatment-related side effects and providing support for the patient’s overall well-being is an integral part of post-treatment care. 

Smoking Cessation: There is evidence that smoking increases the risk of thymomas. As a result, giving up smoking is essential since it can greatly lower the chance of getting malignant tumours.

Furthermore, as secondhand smoke can affect immunological function and general health, it is equally crucial for people with thymoma to avoid it. 

Healthy Diet and Lifestyle: A well-balanced diet can support overall health and may aid in bolstering the immune system’s function.  

Reducing Environmental Toxins: Minimizing exposure to environmental toxins and pollutants whenever possible can be beneficial. This includes avoiding exposure to chemicals, pollutants, and other harmful substances that could potentially affect the immune system or aggravate existing health conditions. 

Stress Management: Participating in stress-relieving practices like meditation, yoga, mindfulness, or accessing counseling or support groups can offer advantages to individuals diagnosed with thymoma. 

Compliance with Medical Recommendations: Following medical advice, adhering to prescribed treatments, attending regular check-ups, and monitoring for any potential recurrence or complications are essential components in managing thymoma. Compliance with medications and therapies as prescribed by healthcare professionals is crucial. 

Corticosteroids 

Case studies have shown that oral glucocorticoid therapy can cause an invasive thymoma to recede. In one instance, the patient’s thymoma and related symptoms completely disappeared, and after a year, there was no radiologic recurrence. 

Multidisciplinary approach 

octreotide 0.5 mg subcutaneously every eight hours used alone or in combination with prednisone 0.6 mg/kg a day was assessed in 38 individuals who had somatostatin receptor-expressing advanced thymomas. 

Out of the total 38 individuals, four patients representing 10.5% exhibited a partial response solely with the administration of octreotide.

Meanwhile, among the subset of 21 patients who were treated with a combination of prednisone & octreotide, two experienced complete responses, while an additional four patients showed partial responses. 

Intervention with procedure 

Surgery is typically the primary treatment for thymomas that have not spread beyond the thymus. The primary objective during surgery is to extract the maximum amount of the tumor whil