Diffuse Large B Cell Lymphoma
Variant: ALK Positive Large B Cell Lymphoma
- Amongst lymphomas, ALK is nearly restricted to primary systemic large cell lymphoma (T lineage)
- A rare set of large B cell lymphomas express ALK
- Large cells with immunoblastic features
- Round nuclei with single large nucleolus
- Binucleate cells common
- One case reported with mixture of large and small cells
- Basophilic cytoplasm, frequently with paranuclear hof
- Frequently sinusoidal
- B lineage based on immunoglobulin expression
- IgA 5/7 cases
- Light chain restriction 6/7
- Based on stains or in situ hybridization
- B lineage markers negative (CD20, CD79a)
- ALK membrane positive, cytoplasm +/-
- Rare cases with clathrin-ALK t(2;17) reported
- t(2;5) not identified
- EMA positive 7/7
- CD30 negative 0/7
- CD45RB weak to moderate positive
- T lineage negative (CD3, CD43, CD45RO)
- CD68 negative
- CD57 positive 5/7
- Aggressive course in 6/7 reported cases
- Note that these are distinct from anaplastic variant of large B cell lymphoma, which is ALK negative
- Large cells with immunoblastic features