Chapter 13: Disorders of the Thymus

Question 1

Thymic hypoplasia or aplasia

Answer 1

• seen in DiGeorge syndrome
• severe defects in cell-mediated immunity
• parathyroid abnormalities as well
• 22q11 deletion syndrome

Question 2

Thymic cysts

Answer 2

uncommon lesions

• seen postmortem if at all
• if you see one though, look for a neoplasm

Question 3

Thymic Hyperplasia

Answer 3

• actually applies to the appearance of B-cell germinal centers within the thymus
• thymic follicular hyperplasia
• most frequently encountered in myasthenia gravis (65%)

Question 4

Thymomas

Answer 4

this definition is restricted to tumors of thymic epithelial cells
-adults older that 40
mediastium

Question 5

noninvasive thymomas

Answer 5

• cells are spindle-shaped

- medullary thymocytes

Question 6

Invasive thymoma

Answer 6

-penetrate through the capsule into surrounding structures

Question 7

Thymic carcinoma

Answer 7

5% of thymomas

• fleshy, obviously invasive
• squamous cell carcinomas
• next most common variant is lymphoepithelioma-like carcinoma
• impingement on mediastinal structures
• the cells that come from this are long-lived CD4 and CD4 t cells
• cortical thymomas rich in thymocytes are more likely to be associated with autoimmune disease