thymomas
Thymoma is the most frequent tumor arising in human thymus.
Types
thymic epithelial tumors
| Types | Traditional (Bernatz) | Kirchner Muller-Hermelink | ||||
| type A | spindle cell thymoma | medullary lypmhoma | ||||
| type AB | combined thymoma | mixed thymoma | ||||
| type B | - | - | ||||
| type B1 | lymphocyte-rich thymoma | predominantly cortical thymoma | type B2 | mixed lymphoepithelioma | cortical thymoma | |
| type B3 | epithelial-rich thymoma | well-differentiated thymic carcinoma | ||||
| type C | thymic acrcinoma (NOS) | other types of thymic carcinoma |
Cytogenetics
chromosome 6 anomalies
- del(6)(p22p25) in type A and type AB thymomas (14499698)
- ring chromosome 6
chromosomes 12 and 16 anomalies
- pseudodicentric (16;12)(q11;p11.2) (type AB or mixed thymoma)
Allelotyping (Loss of heterozygosity (LOH) loci)
- 6q23.3-25.3 (23.5%-45.8%) (12368223)
- 3p14.2 (FHIT gene locus)
- 5q21 (APC)
- 6p21
- 6q21-22.1
- 7p21-22
- 8q11.21-23
- 13q14 (RB)
- 17p13.1 (p53)
Tumorigenetic pathways
APC-associated pathway: 5q21 - 3p22-24.2 - 13q14 - 17p13.1 regions.
type A thymomas: 6q23.3-25.5 only
Microsatellite instability (MSI)
microsatellite instability (MSI): 2.4%-12.5% (12368223) .
- type B3 thymoma only (?)