What is the embrologic origin of the thymus?
third (occasionally fourth) pharyngeal pouch
What age-related changes occur in the thymus ?
-grows from birth to puberty
-reaches max size during puberty
-involutes, becomes replaced with fibrous/fatty tissue, following pubtery
*this involution is accompanied by decreased function
What are causes of thymic involution other than age?
What are the functions of the thymus?
-T cell maturation and development of T cell central tolerance
What developmental abnormalities of the thymus exist?
What is their significance if any?
Thymic hypoplasia (DiGeorge syndrome)
-severe cell-mediated immunte deficits, accompanied by hypoparathyroidism
-benign and frequently incidental findings
-thymic neoplasms can appear similar to cysts; should rule out if experiencing symptoms
-grossly normal size, microscopic hyperplasia of the follicle
-due to germinal centers containing B cells
-can occur in myasthenia gravis and other autoimmune disorders
What is the most common primary cancer of the thymus?
thymoma (neoplasm of thymic epitheliual cells)
What is the common presentation of a thymoma?
-adult >40 y/o; rare in children
-frequently found incidentally in work-up of autoimmune disease (myasthenia gravis)
-signs of impingment of mediastinal structures (40%)
-most commonly located in anterosuperior mediastinum