Thymolipoma
Definition
- Mass forming lesion composed of circumscribed mature adipose tissue and unremarkable thymus
Diagnostic Criteria
- Circumscribed mass forming lesion
- Usually over 500 gm
- Smaller lesions may be found in thymectomy performed for myasthenia gravis
- May form a discrete tumor in thymus or diffusely enlarge the thymus
- Usually over 500 gm
- Predominantly adipose tissue containing interconnecting cords of thymus
- Thymic tissue is essentially unremarkable with both cortex and medulla
- Rare variants are reported, with no known clinical difference
- Thymofibrolipoma
- Lipofibroadenoma
- Interconnecting cords of epithelial cells and groups of adipocytes set in a loose fibrous component
- 2 of 3 reported cases were associated with conventional thymoma
- One case reported as thymohemangiolipoma
- Rare cases reported with prominent myoid cells
- Rare, mean age 20-30
- May be seen in children
- Up to 50% in some series are associated with autoimmune disease
- Myasthenia gravis is most common
- Also aplastic anemia, hypogammaglobulinemia, lichen planus, Grave disease
- Diseases and symptoms may improve following resection
- Myasthenia gravis is most common
- Benign
- Differential diagnosis is limited
- Lipoma is ruled out by the presence of the thymic component
- Atrophic thymus with adipose replacement is an incidental finding and does not form a mass
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
