Diffuse Large B Cell Lymphoma, NOS Flashcards
What is the definition of
DLBCL?
- medium to large B cells growing in sheets
- nuclei are the same size as macrophages or 2x a normal lymphocyte
What is the epidemiology of
DLBCL?
- slightly more common in M > F
- constitutes ~35% of adult non-Hodgkin Lymphomas
- more common in elderly people in 7th decade of life
What is the postulated etiology of
DLBCL, NOS?
- etiology is unknown
- can arise de Novo or as a transformation from a lower grade B cell neoplasm
Note: underlying immunodeficiency is a significant risk factor for developing DLBCL, NOS
- more likely to be EBV positive
What entities can DLBCL arise from?
- CLL/SLL (Richter transformation)
- Follicular lymphoma
- Marginal zone lymphoma
- Nodular Lymphocyte Predominant Hodgkin Lymphoma
What molecular type are EBV + DLBCL?
ABC type
What is the typical localization of
DLBCL, NOS?
- can be nodal or extranodal disease
- 40% are extranodal initially
- most common site:
- GI tract –> stomach, ileocecal region
Note: Primary CNS or testicular DLBCL share similarities because they are from immune priveleged sites
- bone marrow can be discordant or concordant
- peripheral blood involvement by DLBCL is rare
What is the clinical presentation of
DLBCL, NOS?
- rapidly enlarging mass or masses
- B symptoms may be present
- most patients do not have them
What are some microscopic findings in
DLBCL ?
- Lymph nodes
- partial but more often complete effacement
- partial infiltration often interfollicular or sinusoidal (less common)
- Morphology can be very variable
- can even see medium sized cells, which often get misclassified
- IMP: all variants can be admixed with lots of T cells and/or histiocytes
- do not categorize based on this only as TCHRBCL
What are some of the common
morphological variants?
- Centroblastic (most common)
- usually GCB subtype
- Immunoblastic
- usually ABC
- >90% of cells are immunoblastic in morphology
- Must differentiate from plasmablastic lymphoma or extranodal involvement by PCM
- Anaplastic
- may resemble the cells of anaplastic large cell lymphoma
- can mimic an undifferentiated carcinoma
- unrelated to ALK + LBCL
What are some of the rare morphological variants
of DLBCL?
- myxoid stroma or fibrillary matrix present
- pseudorosette formation present
- spindle or signet ring cells
- cytoplasmic granules
- microvillous projections
- intercellular junctions
What is the immunophenotype of
DLBCL, NOS?
- pan-B cell markers + :
- CD19, CD20, CD22, CD79a, and PAX5
- but they can lack one or more of these
- surface and cytoplasmic immunoglobulins
- IgM > IgG > IgA
- cytoplasmic Ig expression does NOT correlate well with expression of CD138
- CD30
- positive in 10%
- often with anaplastic morphology
- EBV
- many are CD30 positive
- if most cells positive should be diagnosed as EBV positive DLBCL
What percentage of DLBCL, NOS
have a positive CD5 IHC?
- 5-10%
- CD5+ DLBCL usually arise de Novo
- differentiated from Blastoid Mantle Cell by:
- lack of cyclin D1 or SOX11 staining
- some may express these markers but not have the CCND1 mutation
- the staining will be much weaker and less uniform
What are the cut off values for positivity
for MYC and BCL2?
- MYC: >40%
- BCL2: > 50%
Note:
- co-expression of these : double expressor
- more frequent in the ABC subtype
What are the cutoffs for CD10, BCL6 and MUM1?
- >30% for each one individually
Note: MUM1 and BCL6 co-expression is seen in 50% of DLBCL
- in normal GCB these are usually mutually exclusive
When is FOXP1 expression often seen
in DLBCL? GCET1? LMO2?
- seen in 20% of DLBCL
- lacking in the GCB phenotype and expressing MUM1/IRF4 and BCL2
- these lack the t(14;18)
- GCET1
- a germinal center marker
- expressed in 40-50% of cases and correlates with GCB
- LMO2
- found in approximately 45% of cases
- highly correlated with germinal center markers
