The thymus gland is responsible for the production of T lymphocytes during the childhood. Neoplasms of the thymus gland arising from its epithelial cells are known as thymomas. On the other hand, thymic carcinomas are the malignant tumors arising from the epithelial cells of the thymus gland. Accordingly, thymic carcinomas are essentially the malignant variant of the thymomas. Thus, the key difference between thymoma and thymic carcinoma is that thymomas are the neoplasms of the thymus gland arising from its epithelial cells whereas thymic carcinomas are essentially the malignant variant of the thymomas.
CONTENTS
1. Overview and Key Difference
2. What is Thymoma
3. What is Thymic Carcinoma
4. Similarities Between Thymoma and Thymic Carcinoma
5. Side by Side Comparison – Thymoma vs Thymic Carcinoma in Tabular Form
6. Summary
What is a Thymoma?
Neoplasms of the thymus gland arising from its epithelial cells are known as thymomas. These tumors characteristically contain benign immature T lymphocytes. There are three main histological varieties of thymomas as,
- Tumors that are cytologically benign and non-invasive
- Tumors that are cytologically benign but invasive or metastatic
- Tumors that are cytologically malignant (thymic carcinoma)
The incidence of thymomas is high among adults who are around 40 years of age. They are rarely seen in children. A majority of thymomas occur in the anterior mediastinum. Neck, thyroid, and pulmonary hilus are the other places that can get thymomas.
Figure 01: An Intrapulmonary Thymoma
Morphology
Noninvasive thymomas are usually made of a mixture of medullary and cortical epithelial cells. There is a nonsignificant thymocyte infiltration. Invasive thymomas predominantly have cortical epithelial cells, and they penetrate into the adjacent structures through the capsule of the gland.
Clinical Features
Most symptoms are due to the impingement of the adjacent structures by the enlarging mass. Dysphagia, cough, chest pain and changes in the voice are the commonest complaints. There is a strong correlation between myasthenia gravis and the incidence of thymomas. There is a significant association with other autoimmune diseases such as Graves disease, Cushing syndrome, pernicious anemia, dermatomyositis, and polymyositis.
Thymomas are treated by the surgical excision of the gland with the neoplastic lesions. This procedure is known as thymectomy.
What is a Thymic Carcinoma?
Thymic carcinomas are the malignant tumors arising from the epithelial cells of the thymus gland. These are fleshy masses with irregular borders, and they usually metastasize to distant sites such as the lungs. Squamous carcinomas and lymphoepithelioma are the commonest cytological varieties of thymic carcinomas. EBV infection is believed to play a role in the pathogenesis of these malignancies due to the presence of EBV genome in the malignant cells.
Figure 02: Thymus Gland
In addition to the symptoms of a benign thymoma, thymic carcinomas can have other constitutional symptoms such as loss of weight, loss of appetite, malaise and bone pain.
Investigations
Thymic carcinomas are usually diagnosed through biopsies
Treatment
Thymectomy and radiotherapy are the therapeutic interventions used in the management of thymic carcinomas.
What is the Similarity Between Thymoma and Thymic Carcinoma?
- All the thymomas and thymic carcinomas arise from the epithelial cells of the thymus gland.
What is the Difference Between Thymoma and Thymic Carcinoma?
Thymoma vs Thymic Carcinoma |
|
| Neoplasms of the thymus gland arising from its epithelial cells are known as thymomas | Thymic carcinomas are the malignant tumors arising from the epithelial cells of the thymus gland. |
| Benign vs Malignant | |
| Thymomas can either benign or malignant. | Thymic carcinomas are always malignant. |
| Symptoms | |
| Most symptoms are due to the impingement of the adjacent structures by the enlarging mass. Dysphagia, cough, chest pain and changes in the voice are the commonest complaints. | In addition to the symptoms of a benign thymoma, thymic carcinomas can have other constitutional symptoms such as loss of weight, loss of appetite, malaise and bone pain. |
| Management | |
| Thymectomy is the first line therapeutic intervention in the management of thymomas. | Thymic carcinomas are treated with thymectomy or radiotherapy. |
Summary – Thymoma vs Thymic Carcinoma
Neoplasms of the thymus gland arising from its epithelial cells are known as thymomas. Thymic carcinomas are the malignant tumors arising from the epithelial cells of the thymus gland. Therefore as their respective definitions imply thymic carcinomas are a malignant subcategory of thymomas. This is the main difference between Thymoma and Thymic Carcinoma.
Reference:
1.Kumar, Vinay, Stanley Leonard Robbins, Ramzi S. Cotran, Abul K. Abbas, and Nelson Fausto. Robbins and Cotran pathologic basis of disease. Philadelphia, Pa: Elsevier Saunders, 2010. Print.
Image Courtesy:
1. “Intrapulmonary thymoma Case 237 (7493571314)” By Yale Rosen from USA – Intrapulmonary thymoma Case 237Uploaded by CFCF (CC BY-SA 2.0) via Commons Wikimedia
2. “Diagram showing the position of the thymus gland CRUK 362” By Cancer Research UK – Original email from CRUK (CC BY-SA 4.0) via Commons Wikimedia