Thymolipoma
Epidemiology and Etiology:
- 2-9% of thymic
neoplasms (rare)
- Unclear etiology:
- Benign tumour of
specialized thymic stroma (fat)
- Aberrant development of the third pharyngeal
pouch
- Fatty regression of a hyperplastic thymus or thymoma
Common sites:
Gross features:
- CT/MRI: predominant areas of mature fat with
interspersed islands of soft tissue
- Encapsulated
- Well circumscribed
- 3 to > 30 cm
- Soft
- Yellow cut surface
Histologic features:
- Mature adipose tissue with strands or large
areas of thymic tissue
- Thymic epithelial component distinguishes thymolipoma
from lipoma
- Thymic
tissue mostly atrophic
- May contain lymph follicles and Hassall
corpuscles
- Rarely may contain thymoma
- No atypia
- No mitotic activity
- Rarely carcinoid contained within
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
- Incidental finding usually
- Local symptoms maybe (cough, dyspnea chest pain,
hoarseness, cyanosis)
- Paraneoplastic syndromes
- Myasthenia gravis (most common)
- Aplastic anemia (rare)
- Graves (rare)
- Hypogammaglobulinemia (rare)
- Complete resection is curative
- No recurrences have been reported
References:
- Travis et al.
WHO Classification of Tumours of the
Lung, Pleura, Thymus, and Heart, 4th ed. (2015)