Mature B cell Neoplasms Part I Flashcards
Define CLL
- Small mature B cells that coexpress CD5 and CD23
- Must have a monoclonal B cell count of greater than or equal to 5 x 109/L
- With the characteristic morphology and phenotype of CLL in the peripheral blood
What is the definition of monoclonal B cell lymphocytosis?
- Clonal CLL count < 5 x 109/L
- Without lymphadenopathy, organomegaly or any other extramedullary disease
What is the definition of SLL?
- SLL and CLL are essentially the same disease…
- Use the term SLL for the following situation:
- circulating CLL count in peripheral blood <5 x 109/L
- there is documented nodal, splenic, or other extramedullary involement
What is the epidemiology of CLL/SLL?
- Most common leukemia of adults in Western countries
- median patient age is 70 years old
- more common in males (2:1)
- Accounts for 7% of non-Hodgkin Lymphomas
- Rare in Asian countries
What tissues are involved by CLL/SLL?
- Blood and bone marrow
- Secondary lymphoid tissues like the spleen, lymph nodes, Waldeyer’s ring
- Extranodal involvement is not common but can occur
- Skin
- GI tract
- CNS
How is CLL/SLL often diagnosed?
- Generally it is diagnosed by routine blood work, occasionally by splenomegaly or lymphadenopathy
- Other manifestations:
- Autoimmune hemolytic anemia
- Immune thrombocytopenia
- Erythroblastopenia
- Pulmonary infections
- Severe allergic reactions to insect bites
- IgM paraprotein (usually)
What is the morphology of CLL/SLL within the lymph nodes?
- Diffuse architectural effacement by proliferation of small B lymphocytes
- Variably scattered paler proliferation centres (pseudofollicles)
- Sometimes have retained variably nodular appearance
- Predominant cells in diffuse areas:
- small lymphocytes with scant cytoplasm
- usually round nucleus with clumped chromatin and occasional nucleolus
What are some of the variations in morphologies that can be seen in CLL/SLL?
- moderate nuclear irregularity can lead to the differential diagnosis of Mantle Cell Lymphoma
- Plasmacytoid differentiation can also be seen
What are the proliferation centres composed of in CLL/SLL?
- continuum of small lymphocytes, prolymphocytes and paraimmunoblasts
- Prolymphocytes:
- small to medium sized
- relatively clumped chromatin and small nucleoli
- Paraimmunoblasts:
- larger with round to oval nuclei, dispersed chromatin
- central eosinophilic nucleolus
- slightly basophilic cytoplasm
What can be seen with large proliferation centres in CLL/SLL?
- these centres are usually large (broader than a 20x field)
- they can also be confluent
- Such cases are usually associated with increased proliferation
- Also deletion of 17p13.1
- Trisomy 12
- More aggressive course
What is the morphology of CLL/SLL in the spleen?
- white pulp involvement is usually very prominent
- red pulp is also involved
- proliferation centres may be seen but are less prominent than in lymph nodes
What is the morphology of CLL/SLL in the peripheral blood?
- Small lymphocytes with clumped chromatin and scant cytoplasm
- Smudge or basket cells are typically seen
- Prolymphocytes can be seen:
- larger with more dispersed chromatin
- irregular nuclear contours
- more abundant cytoplasm
- consistently <15% of the cells
How is atypical CLL defined?
- more prolymphocytes than normal CLL (>15%) but there is still <55%
- Usually these cases are associated with the following:
- Trisomy 12
- Strong positivity for:
- Surface immunoglobulin
- CD20
- FMC7
If you have >55% prolymphocytes what is your diagnosis?
B-cell prolymphocytic leukemia
What is the morphology of CLL/SLL in the bone marrow?
- can have interstitial, nodular, combined or diffuse involvement
- Diffuse involvement usually is seen in more advanced disease
- Paratrabecular aggregates are not typical
- Proliferation centres can be seen
- Most cases have >30% CLL cells in the marrow aspirate
Immunophenotype of CLL/SLL
- Positive for:
- CD19, CD20, CD22 and CD79b
- Dim surface IgM/IgD
- CD5 and CD43
- Strong positive: CD23 and CD200
- Negative for:
- CD10 and FMC7 (may be weakly expressed)
What is the atypical immunophenotype that may be seen with CLL/SLL ?
- Negative:
- CD5 or CD23
- Positive
- FMC7
- Strong surface immunoglobulin
- or CD79b
- In these cases, especially CD5 negative, important to exclude:
- Splenic Marginal Zone Lymphoma
What can the staining be in tissue sections of CLL/SLL?
- cytoplasmic immunoglobulin can stain
- CD20 and CD23 stronger positivity in the proliferation centres vs. the diffuse areas
- LEF1
- almost exclusively positive in CLL/SLL
- not positive in normal B lymphocytes or other lymphomas
Can Cyclin D1 be positive in CLL/SLL?
- YES!
- some positive cells can be seen in proliferation centres in ~30% of cases
- These cells are SOX11 negative
- No chromosomal translocations are seen affecting the CCND1 gene
Note: MYC and NOTCH can also be seen in proliferation centres without gene alterations
What is the postulated normal counterpart to the CLL/SLL cell?
- An antigen-experienced mature CD5+ B cell with mutated or unmutated IGHV genes
What are some of the most common cytogenetic abnormalities identified in CLL/SLL?
- No specific genetic markers
- Most common alterations identified include:
- deletions in 13q14.3 (~50% of cases)
- Trisomy 12 or partial trisomy 12q13 (~20% cases)
- Deletion 11q22-23, 17p13.1 (TP53), or 6q21
- Chromosomal translocations are uncommon in CLL
What is the inheritability of CLL/SLL?
- Familial predisposition can be seen in 5-10% of patients
- Risk of developing CLL is 2-7x higher in first degree relatives with CLL
- Also at risk of other lymphoid neoplasms
What is the name of the clinical staging system used for CLL/SLL?
Rai and Binet are used to define disease extent and prognosis
True or False:
Patients who have CLL/SLL and have the mutated IGHV genes have a better prognosis that those who do not have the mutated gene.
True
The expression of what three markers in CLL/SLL has an adverese prognosis in the disease?
ZAP70
CD38
CD49d
How do the three epigenetic subtypes of CLL/SLL affect the prognosis of the disease?
- Naive-like cases: have the worst prognosis
- Memory-like cases: have the best prognosis
How do deletions of 11q and particularly deletion in 17p affect the clinical outcome of CLL/SLL?
Worse clinical outcome
What is the clinical outcome of deltion 13q14 in CLL/SLL?
Associated with a more favorable clinical course.
- HOWEVER: CLL with a high proportion of cells with isolated 13q deletion do NOT do well.
What gene abnormalities predict a lack of response to Fludarabine-containing regimes in CLL/SLL?
- TP53 abnormalities:
- Deletion of 17p13.1
- TP53 mutations
- These mutations must be checked before starting any type of therapy in these patients.
Additional adverse predictive factors for CLL/SLL
- Complex karyotype: poor outcome
- rapid lymphocyte doubling in the blood (<12 months)
- elevated serum markers of rapid cell turnover:
- thymidine kinase
- beta-2 microglobulin
What other mutations in CLL have been associated with a poor outcome?
- TP53
- ATM
- NOTCH1
- SF3B1
- BIRC3
What features of CLL/SLL are suggestive of clinical progression or histologically more aggressive lesions?
- Increase in size of proliferation centres of the lymph nodes
- Higher proliferation rate with confluent centres
- Broader than a 20x field
- Ki67 >40% or >2.4 mitosis in the proliferation centres *
- Higher proliferation rate with confluent centres
- Prolymphocytoid Transformation: more prolymphocytes in the blood
Note: ** this needs more data to be supported
Note: these cases have an outcome intermediate between Richter transformation (DLBCL) and traditional CLL
Does CLL ever transform into B-cell prolymphocytic leukemia?
No
By definition these are two separate entities and CLL does NOT transform into this.
What diseases can CLL transform into and what is the prognosis?
- DLBCL (~2-8% of cases)
- Classic Hodgkin Lymphoma (<1%)
-
RICHTER Syndrome: cases of DLBCL that are clonally related to the previous CLL
- Express the same immunoglobulin gene rearrangement and are IGHV-unmutated
- Clonally unrelated CLL and DLBCL usually occur in IGVH mutated CLL
What is the prognosis of Richter transformation DLBCL in patients with CLL?
Median survival is <1 year
What is the prognosis of CLL with an unrelated, de novo DLBCL?
Prognosis is that of de novo DLBCL
What mutations is DLBCL transformation from CLL associated?
TP53 mutation
NOTCH1 mutation
CDKN2A deletions
MYC translocation
In what situation does Hodgkin Lymphoma develop in patients with CLL/SLL?
- Mutated CLL
- Hodgkin lymphoma cases are EBV positive
- Hodgkin cases are unrelated to the CLL clone
What is required to make the diagnosis of Hodgkin Lymphoma in the setting of CLL?
- Classic Reed-Sternberg cells in an appropriate background of cells
Note: the presence of EBV positive or sometimes negative RS cells only is not enough to call Hodgkin lymphoma.
What is the definition of a monoclonal B-cell lymphocytosis (MBL)?
- Monoclonal B-cell count <5 x 109/L in the peripheral blood
- NO associated lymphadenopathy, organomegaly, other extramedullary involvement
- No other features of lymphoproliferative disorder
IMP: remember that many small B-cell lymphomas and leukemias have low-level peripheral blood involvement
What are the three categories of Monoclonal B cell lymphocytosis?
- CLL-type
- Atypical CLL-type
- non-CLL type
Discuss the features of MBL with CLL-type
- Most common type of MBL (~75% of cases)
- Characterized by coexpression:
- CD19, CD20 (dim), CD5 and CD23
- B cells show light chain restriction or >25% lack surface immunoglobulin
- More than 1 clone may exist
- Frequency increases with age and all CLL cases develop from MBL but not all MBL proceed to CLL
CLL-type MBL can be further classified how?
- Further divided by the size of the monoclonal population
- Low-count (<0.5 x109/L)
- High-count (>0.5x109/L)
- Low-count is biologically different and does not seem to progress to frank CLL
- High-count has biological features similar to CLL and progresses to frank leukemia at an annual rate of 1-2% per year
What is the definition of MBL with an atypical CLL phenotype?
- Express:
- CD19, CD20(bright), CD5
- CD23 can be negative!
- moderate to bright surface Ig
CRITICAL: to exclude a Mantle Cell Lymphoma or other B-cell lymphoma in these cases
What is the definition of MBL with a non-CLL phenotype?
- CD5 (-) or CD5 (dim)
- CD19 and CD20 (+)
- Moderate to right surface immunoglobulin expression
Note:
- some clones may be transient or self-limited
- upt to 17% may eventually develop splenomegaly, suggesting a relationship to Splenic Marginal Zone lymphoma
What is the definition of B-cell Prolymphocytic Leukemia?
- B-cell neoplasm composed of >55% of prolymphocytes within the peripheral blood
- Involves other areas including:
- bone marrow
- spleen
Why are cases of CLL with increased prolymphocytes and lymphoid proliferations with relatively similar morphology but a t(11;14)(q13;q32) [IGH/CCND1] translocation OR SOX11 excluded from the definition of B-cell prolymphocytic leukemia?
They are essentially Mantle Cell Lymphoma with leukemic expression.
What is the incidence and median age of presentation of B-PLL?
- represents about 1% of lymphocytic leukemias
- usually seen in patients >60 years old
Where are the leukemic cells localized in B-PLL?
- peripheral blood
- bone marrow
- spleen
What are the clinical feature of B-PLL?
- B symptoms
- Massive splenomegaly
- Absent or minimal peripheral lymphadenopathy
- Rapidly increasing lymphocyte count
- >100 x 109/L
- Anemia and thrombocytopenia are seen in 50% of cases
What are the microscopic findings in the peripheral blood in B-PLL?
Peripheral Blood
- Majority of circulating cells are prolymphocytes
- >55%, but usually >90%
- Medium sized lymphocytes
- 2x the size of a normal lymphocyte
- Round nucleus, moderately condensed nuclear chromatin, and prominent central nucleolus
- some cases the nucleus can be indented
- Relatively small amount of faintly basophilic cytoplasm
What are the microscopic findings in the bone marrow in B-PLL?
- interstitial or nodular intertrabecular infiltrate
- lymphoid cells are similar to those seen in the peripheral blood
What are the microscopic findings in the spleen in B-PLL?
- expanded white pulp nodules
- red pulp infiltrate
- intermediate to large cells
- abundant cytoplasm, irregular round nuclei and prominent eosinophilic nucleolus
What are the microscopic findings in the lymph nodes in B-PLL?
- diffuse or vaguely nodular infiltrate by cells similar in appearance to those in the spleen
- proliferation centres (pseudo-follicles) are not seen
True or False
The diagnosis of B-PLL can be made easiy on morphologic grounds?
False
- No specific markers for B-PLL
- Diagnosis of B-PLL cannot be made without excluding the following diseases:
- pleomorphic mantle cell lymphoma
- splenic marginal zone lymphoma
- CLL with an increased number of prolymphocytes
What is the immunophenotype of B-PLL?
- strongly express surface IgM/IgD
- B cell antigens (strongly expressed)
- CD19, CD20, CD22, CD79a, CD79b, and FMC7
- CD5: positive in only 20-30% of cases
- CD23: positive in only 10-20% of cases
- CD200: weakly positive or negative
Does B-PLL show CD38 and ZAP70 expression?
- 50% of cases show expression of the antigens
- ZAP70 expression does NOT correlate with IGHV mutation status
What is the postulated normal counterpart for B-PLL?
- A mature B cell of unknown type
Is t(11;14)(q13;q32) identified in B-PLL?
- NO
- These are considered to be leukemic forms of Mantle Cell Lymphoma
What cytogenetic abnormalities have been identified in B-PLL?
- Complex karyotypes are common
- Deletions in 17p13 are detected in 50% of cases
- these are associated with TP53 mutations
- This likely underlies the progressive course of B-PLL and relative treatment resistance
- Deletions of 13q14 are seen in 27% of cases
- Trisomy 12 is uncommon
- Aberrations of MYC including gains, amplifications and translocations are reported
- IMP: B-PLL has a transcriptional profile that is different from CLL
What is the prognosis of B-PLL and are there any predictive factors ?
- Median survival: 30-50 months
- B-PLL responds poorly to therapies for CLL
-
NO Correlation between survival and the following:
- ZAP70 expression
- CD38 positivity
- Deletion 17p
- IGHV mutation status
- splenectomy may improve symptoms
What is the definition of splenic marginal zone lymphoma?
- Small, B-cell neoplasm
- Lymphocytes replace the splenic white pulp germinal centres
- efface the follicle mantle
- merge with the peripheral (marginal) zone of larger cells
- scattered transformed blasts are present
- small and large cells infiltrate the red pulp
What other sites can and often does splenic marginal zone lymphoma involve?
- splenic hilar lymph nodes
- bone marrow
- lymphoma cells are often found in the peripheral blood as villous lymphocytes
- Note:
- the liver can often be involved as well
- the peripheral lymph nodes are NOT involved
What is the epidemiology of splenic marginal zone lymphoma (SMZL)?
- represents <2% of all lymphoid neoplasms
- but it may be a significant portion of otherwise unclassifiable CLL cases that are CD5 negative
- usually seen in patients >50 years old
- women and men are equally affected
What is the clinical presentation of SMZL?
- Splenomegaly
- often have autoimmune thrombocytopenia and anemia
- bone marrow is frequently involved
- 1/3 of patients have a small paraprotein
- hyperviscosity and hypergammaglobulinemia are rare
- IMP: there is an association between SMZL and Hepatits C virus in southern Europe
What are the microscopic findings of SMZL in the spleen?
- splenic white pulp has a central zone of small, round lymphocytes often replacing any germinal centers
- the normal mantle is effaced as well
- merge with a peripheral zone of medium-sized lymphocytes
- cells have dispersed chromatin and abundant pale cytoplasm
- resemble marginal zone cells
- transformed blasts are also present
- cells have dispersed chromatin and abundant pale cytoplasm
What does the red pulp look like in SMZL?
- red pulp is always infiltrated by nodules of larger cells and sheets of small lymphocytes
- often invade the sinuses
- Epithelioid histiocytes can be present within the lymphoid aggregates
True or False:
Plasmacytic differentiation is seen in SMZL?
TRUE
- plasmacytic differentiation can occur
- RARELY clusters of plasma cells can be seen in the centre of the white pulp nodules
What are the microscopic findings of SMZL in the splenic hilar lymph nodes?
- sinuses are dilated and lymphoma cells surround the germinal centres
- unlike in the spleen
- the lymphoma cells and more marginal-zone like cells are more intimately intermixed
- there is no formation of the so-called marginal zone
What are the microscopic findings of SMZL in the bone marrow?
- nodular interstitial infiltrate, cytologically similar to that seen in the lymph nodes
- sometimes neoplastic cells surround reactive follicles
- intrasinusoidal lymphocytes are more evident after staining with CD20
- IMP:
- peripheral blood cells have short polar villi
- sometimes can look plasmacytoid
What is the differential diagnosis of SMZL?
- CLL
- Hairy cell leukemia
- Mantle Cell Lymphoma
- Follicular lymphoma
- Lymphoplasmacytic lymphoma
What are important things to remember when thinking of the differential for SMZL?
- Many small B cell lymphomas can have slightly larger cells with pale cytoplasm when they involve the splenic marginal zone (mimic SMZL)
- Nodular infiltration pattern in bone marrow excludes hairy cell leukemia
What is the immunophenotype of SMZL?
- express surface IgM and usually IgD
- Positive
- CD20, CD79a
- Negative
- CD5 and CD10
- CD23 and CD43
- Annexin 1
- CD103 and cyclin D1
- Ki67 usually in a targetoid pattern
- positive in GC and marginal zone
The absence of staining of cyclin D1 and LEF1 in SMZL is helpful in excluding which two entities?
- Cyclin D1: Mantle Cell Lymphoma
- LEF1: CLL
The absence of staining of Annexin 1, CD10 and BCL6 in SMZL helps exclude which entities?
- Annexin 1: Hairy Cell Leukemia
- CD10 and BCL6: Follicular Lymphoma
IMP: a group of CD5+ SMZL cases has been described and are characterized by a higher lymphocytosis and diffuse bone marrow infiltration.
What is the postulated normal counterpart of SMZL?
Marginal Zone B cell
may or may not demonstrate evidence of antigen exposure
What are the key cytogenetic abnormalities seen in SMZL?
- SMZL lacks recurrent chromosomal translocations which makes identification of such useful in diagnosing other B cell lymphomas that may mimic SMZL
- Small number show t(2;7)(p12;q21) translocation
- activates the CDK6 gene
- 30% SMZL have heterozygous deletion of 7q
- rarely found in other lymphomas
- Gain of 3q is seen in a good subset
What two genes are frequently mutated in SMZL that give a hint as to the pathogenesis of the disease?
NOTCH2
- one of the most frequently mutated (10-25%)
- also seen in other B cell lymphomas
KLF2
- somatically mutated in 10-40% of cases
- also seen in other B cell lymphomas
Both mutations are seen with cases with deletion 7q
The genes are physiologically inovlved in proliferation and commitment of mature B cells to the marginal zone, points to homing to the spleen compartments and marginal zone differentiation
Presence of MYD88 mutations point to which entity instead of SMZL?
Lymphoplasmacytic lymphoma
Note: although rarely SMZL can have this mutation.
Presence of t(14;18)(q32;q21) translocation points to which entity rather than SMZL and what are the genes?
- Follicular Lymphoma
- affects BCL2
Presence of t(11;14)(q13;q32) translocation points to which entity rather than SMZL and what are the genes?
- Mantle Cell Lymphoma
- CCND1
Presence of t(11;18)(q21;q21), t(14;18)(q32;q21), and t(1;14)(p22;q32) translocation points to which entity rather than SMZL and what are the genes?
- Extranodal Marginal Zone Lymphoma of Mucosa-Associated Lymphoid Tissue (MALT Lymphoma)
- Genes (respective to each translocation)
- t(11;18)(q21;q21): BIRC3-MALT1
- t(14;18)(q32;q21): IGH/MALT1
- t(1;14)(p22;q32): IGH-BCL10
What is the prognosis of SMZL?
- clinical course is indolent with a 10 year survival of 67-95%
- Repsponse to chemotherapy often used for other B cell lymphomas is poor
- Patients often respond (hematologically) to splenectomy and Rituximab with long-term survival
- Transformation to Large B cell lymphoma occurs in 10-15% of cases
Does SMZL associated with Hepatitis C virus infection respond to antiviral treatment?
- YES
- Treatment with Interferon gamma with or without Ribavirin has been shown to be effective in treating SMZL
What are some adverse prognostic factors in SMZL?
- large tumor mass
- poor general health status
- NOTCH2, KLF2, and in particular TP53 mutations
Note: a clinical scoring system has been proposed that looks at the following to risk stratefy:
- Hgb concentration
- Platelet count
- Lactate dehydrogenase
- Extrahilar lymphadenopathy
What is the definition of Hairy Cell Leukemia?
- Indolent
- small mature B lymphocytes
- oval nuclei and abundant cytoplasm with hairy projections
- involves the peripheral blood and diffusely infiltrates the bone marrow and splenic red pulp
What is the epidemiology of Hairy Cell Leukemia?
- Rare disease, accounts for only 2% of all lymphoid leukemias
- Annual incidence rate: 0.32 per 100,000
- Median age of presentation is 58 years of age
- Rare in patients in their 20s
- Very uncommon diagnosis in children
- More common in males (4:1)
- More common in whites than in blacks
What is the disease defining molecular alteration in Hairy Cell Leukemia?
- BRAF V600E
- This mutation leads to a constituitive activation of MAPK
- This mutation is present in 100% of cases
What are the sites of involvement for Hairy Cell Leukemia?
- Lesions are predominantly found in the bone marrow and spleen
- Typically a small number of tumor cells can be found circulating in the peripheral blood
- Tumor infiltrates can be noted in the liver and the lymph nodes (rarely)
- Occasionally in the skin
- Very rarely patients can present with abdominal lymphadenopathy
