The thymus gland is fairly large in infants and young children because it is essential in the early years for the development and maturation of their immune system. The T lymphocytes must mature in the thymus to be able to help protect the body against foreign substances. The gland grows until children have almost reached puberty, and then it slowly decreases in size, with much of its tissue being replaced by fat.
Thymoma
The mediastinum is the area of the body that includes the thymus, heart, trachea and esophagus. A thymoma is a tumor of the thymus. It is the most common tumor of the mediastinum, according to the Katie Nason, M.D., Assistant Professor at the University of Pittsburgh Medical Center and author of a chapter in "Schwartz's Principles of Surgery." Most people with a thymoma are 40 to 60 years old. Some of them may not have any symptoms, but others may have night sweats, wheezing, difficulty breathing, weight loss, fever, chest pain, fatigue and cough.
Persons with myasthenia gravis, a disease that causes muscle weakness, are at increased risk for having a thymoma. Thus, they are always checked for this type of thymus gland disease. However, Dr. Nason notes that when these individuals have a CT scan, less than 10 percent actually have a thymoma.
Thymolipoma
A thymolipoma is a rare tumor of the thymus gland. It is a benign tumor, which means it does not invade or infiltrate any nearby tissues or organs. It is also a fatty tumor, with separate areas of thymus tissue spread out among the fat tissue. Dr. Nason writes in "Schwartz's Principles of Surgery" that thymolipomas can become very big and notes that even people with large tumors still may not have any symptoms.
Thymic Hyperplasia
The term hyperplasia means an increase in the number of cells within an organ, which results in a larger organ. In thymic hyperplasia, the thymus gland is larger than normal. Sometimes, physicians use the term "rebound thymic hyperplasia." This describes the thymus gland of adults who have had chemotherapy for lymphoma, or a tumor of the lymphoid tissue. After chemotherapy, the thymus gland is smalle, because the medication makes the gland shrink in size. After a period of time, however, the gland grows. Dr. Nason writes that it usually becomes large approximately nine months after people have stopped taking chemotherapy, but the gland can grow large in just two weeks or any time from two weeks up to a year.
Thymic Carcinoma
Thymic carcinomas are malignant tumors. They invade nearby tissues and organs or spread to distant sites. These tumors invade nearby tissues much earlier than thymomas and they involve several different types of cells, according to the book "Robbins Pathologic Basis of Disease." Most people with thymic carcinomas are older than 40 years.
References
- "Robbins Pathologic Basis of Disease"; Ramzi Cotran, M.D., Vinay Kumar, M.D., Stanley Robbins, M.D.; 1994
- "Schwartz's Principles of Surgery"; F. Charles Brunicardi, M.D.; 2010
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