Primary Mediastinal (Thymic) Large B Cell Lymphoma
Supplemental Studies
Immunohistology
- B lineage is required for diagnosis
- CD20 and or CD79a pos
- Immunoglobulin frequently negative, even with frozen tissue or on flow, although immunoglobulin genes are rearranged
| CD5 |
Neg |
| CD10 |
33% |
| bcl6 |
100% |
| CD30 |
69% |
| CD15 |
4% |
- Keratin may highlight overrun or hyperplastic thymus
- Reported in 40% of cases with adequate tissue
- HCG has been reported in one case
- 10 other cases tested were negative
Genetic Study
- Immunoglobulin gene rearrangements are present, even in cases in which immunoglobulin is not demonstrable
- Cytogenetics infrequently useful
- Gains of chromosomal material are more common than losses
- However, gain of chromosome 9p, seen in a minority of cases, is the only non-random karyotypic alteration
