Thymic Cyst
Definition
- Epithelial lined cyst involving the thymus
Diagnostic Criteria
- Frequently separated into congenital and aquired types
- Common features
- May occur at all ages
- May be found in neck or mediastinum
- Thymic tissue must be present at least focally within the wall of the cyst
- Congenital type
- Thin wall
- May be unilocular or multilocular
- Lined by squamous, glandular or ciliated epithelium
- Acquired type
- Walls thickened by inflammatory infiltrate
- May have germinal centers
- Virtually alwalys multilocular
- Lined by squamous or columnar epithelium
- May exhibit pseudoepitheliomatous hyperplasia
- Frequent cholesterol clefts and granulomas
- One report of four patients with associated fever and autoimmune disease (Izumi)
- Cured by resection
- May be associated with any neoplasm, but most frequently with:
- Thymoma
- Cysts usually lack epithelial lining
- Basaloid thymic carcinoma
- Lymphoma, Hodgkin or extranodal marginal zone
- Germ cell tumor, especially seminoma
- Close inspection and immunohistochemistry may be required
- Thymoma
- Walls thickened by inflammatory infiltrate
- Common features
- Both types are benign (if not associated with a neoplasm)
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
