differential diagnosis of CLL

1. B Cell Disorders Other
than CLL
Dr. Umme Habiba

3. Significance:
• NHL in leukaemic phase can mimic CLL:
• mantle-cell lymphoma,
• Lymphoplasmacytic lymphoma
• Marginal zone lymphoma.
• CLL(small percentage (i.e. 1–10%) of atypical lymphocytes (e.g. prolymphocytes, lymphoplasmacytoid
cells, cleaved cells or centrocytes) can be present in blood.
• CLL/PL: percentage of atypical cells is >10% but <55%, CLL with prolymphocytoid cells is accepted as
an atypical variant of CLL.
• Lymphoplasmacytic lymphoma(Waldenstrom’s macroglobulinaemia): is characterized by a
proliferation of an admixture of small lymphocytes, plasmacytoid lymphocytes and plasma cells;
monoclonal IgM peak is a hallmark of the disease. (exclusion of otherB-cell disorders with plasmatic
differentiation). MYD88(L265P) mutations in nearly all patients, and mutations of CXCR4 in
30%ofcases.
• The presence of more than 55% prolymphocytes is a feature that arbitrarily defines B-cell
prolymphocytic leukaemia(B-PLL),an extremely infrequent disorderthat in most cases corresponds to
mantle-cell lymphoma (MCL) in leukaemic phase. In fact B-PLL is a morphological diagnosis, may
represent either poor-riskCLL or MCL, and is probably not a discrete entity in its own right. CLL does
not evolve to B-PLL.

4. Diagnosis of CLL-related conditions
• Monoclonal B-cell lymphocytosis (MBL)
• Absence of lymphadenopathy, organomegaly (detected clinically or radiologically),
cytopenias and clinical symptoms,
• < 5× 10 9/L monoclonal B lymphocytes in blood with a CLL phenotype is defined as MBL
• Small lymphocytic lymphoma (SLL)
• Presence of lymphadenopathy or organomegaly (detected either clinically or by imaging
studies),cytopenias or other disease-related features
• <5× 10 9/L B lymphocytes in blood.
• Immunophenotype same as CLL
• Richter’s syndrome (RS)
• Development of an aggressive lymphoma, most commonly a diffuse large B-cell
lymphoma(DLBCL)in a patient previously(or simultaneously) diagnosed with CLL.
• The biopsy of a lymph node or another lymphoid tissue is mandatory

8. Other B-cell chronic disorders
• B-cell prolymphocytic leukaemia
• The diagnosis is mainly based on morphology and cell markers.
• The main diagnostic criterion is : percentage of prolymphocytes >55% in
peripheral blood. (Prolymphocyte= 2x size of a small CLL lymphocyte with
moderately condensed nuclear chromatin, a prominent central nucleolus and
a lower N/C ratio than CLL cells.
• The mean age: 70 years
• Presenting complain: splenomegaly without lymphadenopathy and a high
WBC count, usually >100 × 109/L. Anemia and thrombocytopenia in 50%.
• Incidence of monoclonal band higher than CLL.

10. Other B-Cell chronic disorders
• Hairy-cell leukaemia (HCL):
• 3% of all leukaemia
• Affects males more frequently than females (ratio 4:1), age> 60years.
• Pancytopenia in most patients present.
• Anaemia is due to the reduced bone marrow production and splenic pooling; with
constant raised MCV; haemolysis is exceptional.
• WBC count: low, normal or high(rarely above 20 × 109/L), but neutropenia and
monocytopenia are constant. Patients with low WBC count and no circulating hairy cells
present diagnostic problems, a bone marrow biopsy being necessary for diagnosis.
• Platelet counts: below 100 × 109/L in most cases.
• HCL should be considered in the differential diagnosis of any single patient with
pancytopenia.

11. Hairy-cell leukaemia
• Physical sign: splenomegaly(main).
• Lymphadenopathy rare at diagnosis ,present in advanced HCL.
• Routine CT hitherto suspected of large abdominal nodes. These are
more common in relapsed patients and those with long-standing HCL
and tend to correlate with bulky disease at presentation.
• The recognition of typical hairy cells in peripheral blood films is
suggestive of diagnosis. However, since the number of hairy cells in
blood is usually low, a high degree of suspicion is required to make
the diagnosis, and ultimately a bone marrow biopsy is required.

14. • Hairy cells: large, twice the size of a normal lymphocyte, and have
abundant cytoplasm(low N/C) that is characteristically villous in its outline
The nucleus is round, oval or slightly indented, and occasionally bilobed. A
smooth nuclear chromatin, absence of a visible nucleolus and low N/C
ratio are hallmarks of typical hairy cells.
• Cells from the rare HCL variant have similar cytoplasmic features, but have
a round nucleus with more condensed chromatin and a distinct nucleolus
• Immunophenotype: includes pan-B cell markers(CD19, CD20,CD22) with
co-expression of CD11c, CD25, CD103, CD123 and CD200. BRAF mutations
are a typical feature.
• Bone Marrow Aspirate: In a characteristic manner, bone marrow aspirates
are unsuccessful, as no fragments and few cells are obtained.

17. • Trephine biopsy: is essential. It shows diffuse interstitial infiltration of variable
degree; occasionally the infiltration is focal
• A typical feature is the arrangement of the cellular infiltrate, which is loose,
leaving plenty of space between cells, often with a clear zone around each cell,
which is unique to this condition
• Reticulin: increased and the cells stain strongly with anti-CD20.
• Hypocellular bone marrows can be observed, which along with the
pancytopenia may raise the possibility of aplastic anaemia as a diagnosis.
• In cases with hypoplastic marrows, immunohistochemistry (e.g. CD20,
annexin1, DBA44, CD11c) is important for demonstrating clusters of hairy cells,
as it is in assessing response after therapy.
• Tartrate-resistant acid phosphatase (TRAP):+ve.

18. • Spleen histology: distinct diagnostic features: infiltration by mononuclear cells
with a blunt nucleus in the red pulp with little residual white pulp, and formation
of pseudo-sinuses filled with erythrocytes.
HCL variant (HCLv):
• is very rare.
• High WBC count (50–80 × 109/L) and splenomegaly.
• The cells are irregular, large nucleolated villous cells
• Immunophenotypically, negative for CD25,CD123 or CD200 and the MCV is
normal.
• The main diagnostic difficulty in HCL variant is with SMZL, except for spleen
histology, which in the former mainly involves the red pulp and in the latter the
white pulp.
• HCLv: regarded as a formof splenic small cell lymphoma/leukaemia, which along
with splenic diffuse red cell lymphoma, is pending further characterization.

20. The leukaemic phase of indolent NHL
• Follicular lymphoma
• Splenic marginal zone lymphoma
• Mantle cell lymphoma

21. Follicular lymphoma
• Around 15% of patients with follicular lymphoma may have circulating
lymphoma cells (5–20 × 109/L), and this correlates with bone marrow
involvement.
• % of patients with inconspicuous blood involvement is much higher, as
demonstrated by flow cytometry or molecular techniques (BCL-2
detection).
• A minority of patients may present with a WBC count in excess of 40 × 10
9/L (up to 200 × 10 9/L) and extensive disease, generalized
lymphadenopathy, hepatomegaly and a prominent splenomegaly.
• Usually the circulating cells are very small, with almost no visible
cytoplasm, the nuclear chromatin is smooth without clumps of
heterochromatin and no visible nucleolus, and the nuclear shape is angular
and has a small cleft

22. • Lymph node histology: essential for confirming a diagnosis of follicular
lymphoma.
• Patients with very high WBC counts may have a poor prognosis;
• Cases with a minor degree of spill-over behave better,as do cases
without circulating cells.
• Late-stage follicular lymphoma may have circulating blasts
(centroblasts) characterized by a peripherally located nucleolus,and
this corresponds with histological transformation to a large-cell
lymphoma or the so-called blastic form of follicular lymphoma

24. Splenic marginal zone lymphoma
• 2/3rds of patients with splenic marginal zone lymphoma (SMZL) (1–2% of all lymphomas)
have circulating villous lymphocytes. A minority does not have frankly villous cells despite
being clonal, and diagnosis can only be established after splenectomy.
• The median age: 70years
• Present with splenomegaly.
• Anaemia and/orthrombocytopenia are seen in 40% of cases.
• 1/3rd have a serum monoclonal band, usually IgM below30g/L.
• An association with hepatitis C; mixed cryoglobinemia. Interferon-α induce CR in some
hepatitis-C-positive SMZLpatients.
• An association with hyperreactive malaria and tropical splenomegaly has been described in
African cases.
• Typical blood film showing small lymphocytes with an irregular membrane outline and short
villi, often confined to one pole of the cells.
• Immunophenotype: SMZL cells are negative for CD103 and CD123 but are always positive
for CD11c.

26. • Bone marrow aspirates may show the same cells as in the blood, with
variable degrees of infiltration.
• A distinct pattern of intra-sinusoidal infiltration is characteristic of
SMZL, which can be highlighted with anti-B-cell
antibodies(CD20,CD79a).
• This pattern of infiltration is less common in other types of NHL and is
not seen in CLL. In addition, the pattern of bone marrow infiltration
can be nodular, interstitial and/or paratrabecular.

27. • The spleen histology shows a characteristic bizoned pattern in the
white pulp, with a central zone of small lymphocytes with scanty
cytoplasm and a peripheral zone of larger cells with more dispersed
chromatin and more abundant cytoplasm. The red pulp is always
infiltrated by both the smaller and the larger cells.

28. Mantle cell lymphoma
• Blood and bone marrow involvement are common in MCL and can be demonstrated
in almost 100% of cases if sensitive enough flow cytometry and
immunohistochemical techniques areused.
• > 40% ofcases evolving with splenomegaly have significant lymphocytosis,
sometimes mimicking atypical CLL
• The presence of blastic cells and high labelling by Ki-67 are the most important
prognostic factors marker.
• Blood film: The cells are medium size,slightly irregular in shape and have a speckled
nuclear chromatin pattern.
• Immunophenotype: MCL cells are always positive for CD5,CD19 and CD20,but
negative for CD23 and also CD200.
• The bone marrow biopsy:monotonous infiltration by slightly irregular cells. In
contrast with CLL, no proliferating centres are seen in MCL