17. Mature B-cell neoplasms Flashcards
What is the difference between CLL and SLL?
Same disease but…
Chronic Lymphocytic Leukaemia - abnormal lymphocytes in blood
Small Lymphocytic Lymphoma - abnormal lymphocytes in lymph nodes
How is CLL characterised at the cellular level?
Accumulation of mature B cell lymphocytes in blood, BM, spleen, lymph nodes
CD5+
Which cytogenetic techniques are used in the diagnosis of CLL and why?
Karyotyping is limited due to low mitotic activity of leukaemic cells in vitro - may miss clonal chromosomal abnormalities
FISH on uncultured interphase cells - identify abnormality in larger proportion of CLL cases (80% vs 50%)
What are the most common chromosomal abnormalities in CLL?
What are the prognoses?
Deletion 17p (TP53) - poor
Deletion 11q (ATM) - poor
Deletion 13q14 - favourable
Trisomy 12 - intermediate
What molecular testing is required in CLL?
TP53
IGVH somatic hypermutation analysis
What prognoses are associated with IGHV SHM?
Mutated IGHV = less aggressive, longer time to first treatment
Un-mutated IGHV = more aggressive, earlier TTFT
What is the purpose of VDJ rearrangments?
Part of adaptive immunity
Rearrangments of VDJ segments in immunogloblin heavy chain form repetoire of unique antibodies (immunogloblin) needed for immunity
What are the VDJ regions?
Regions of the immunogloblin heavy gene loci
Variable (66, 44 functional)
Diversity (27)
Joining (6)
What is the purpose of somatic IGH hypermutation?
Takes places after VDJ recombination
Adds/deletes nucleotides - adds to the number of unique immunoglobins needed for immunity
How is IGH hypermutation tested for?
Sanger sequencing
F primers 5’ of each of the 7 different V families
Common R primer (JHCONS) binds to homologous region 3’ of each J segment
Sequence data uploaded to IMGT/ARREST - determine which V, D, J segments are present
Sequence compared to germline to determine mutation level
Which V family segments are most frequently used?
V3
V4
V1
What constitues a mutated and unmutated result?
Unmutated = >98% similarity to germline sequence
Mutated = <98
What information does IGH sequencing give, other than % simililarity?
19 defined stereotypes in CLL, 4 provide prognostic info:
1 - aggressive disease
2 - poor prognosis regardless of mutation status
3 - indolent CLL, good prognosis
4 - aggressive, risk of Richter’s transformation (into DLCBL)
What is the phenotype of CLL?
Often asymptomatic at diagnosis
Fatigue, haemolytic anaemia, splenomegaly
High inherited predisposition
What is the course of disease in CLL?
Highly variable
Near normal life expectancy to rapid progression & early death
What often occurs before and after CLL?
Before - Monoclonal B-cell lymphocytosis (MBL) (pre-malignant condition)
After - Richter’s transformation into aggressive DLBCL in 5-15% of cases
Name 3 other genes that are commonly mutated in CLL? Why are they useful?
NOTCH1
SF3B1
BIRC3
Don’t guide therapy but represent markers for progression & survival
How is multiple myeloma characterised?
Accumulation of clonal plasma cells in BM
What is the phenotype of multiple myeloma?
CRAB:
hyperCalcaemia
Renal failure
Anaemia
Bone disease
How is multiple myeloma sub-divided genetically? What is the prognosis of each?
Hyperdiploid - 48-75 chr, gains of odd no. chr
Favourable prognosis
Non-hyperdiploid - translocations involving IGH (chr 14)
Poor prognosis
How is MM tested for?
Analysis of metaphase chromosomes is problematic due to the low spontaneous proliferative activity of these cells in vitro
Therefore interphase FISH for poor prognostic rearrangements
What must be done prior to FISH testing in MM and why?
Cell selection of plasma cells to ensure myeloma cells are examined - avoids false negative result
Done by magnetic-activated cell sorting using CD138+ antibodies
