Chronic lymphocytic leukaemia (CLL) / small lymphocytic lymphoma (SLL)

Definition

A neoplasm of small round B-lymphocytes in the peripheral blood, bone marrow and lymph nodes, admixed with prolymphocytes and paraimmunoblasts (pseudofollicles), usually expressing CD5 and CD23. SLL is applied to those cases non-leukaemic with the same morphology

Synonyms

Epidemiology

B-CLL constitutes 90% of cases of chronic lymphoid leukaemia. Most patients are more than 50 years old, with a male predominance of 2:1.

Clinical features

Typical sites of involvement are lymph nodes, liver, spleen, skin, breast and ocular adnexa. Patients are commonly asymptomatic but may present with fatigue, autoimmune haemolytic anaemia, infections, hepatosplenomegaly or extranodal infiltrates.

Histopathology

The nodal architecture is replaced by a pseudofollicular pattern of pale areas composed of larger cells in a darker background of small cells. The pseudofollicles (proliferation centres, growth centres) contain a continuum of small, medium (prolymphocytes) to large (paraimmunoblasts) cells. The spleen shows predominantly white pulp involvement; pseudofollicles are less prominent. Some cases show plasmacytoid differentiation. Bone marrow involvement may be nodular, interstitial, diffuse or mixed. A paratrabecular distribution is not typical. Pseudofollicles are not common but may be found.

Immunohistochemistry

CD5

usually positive

 

CD10

negative

CD11c

positive (weak)

CD19†

positive

CD20

positive (weak)

CD22

 positive(weak)

CD23†

usually positive

CD38

may be positive in cases with unmutated Ig variable region genes

CD43

positive

CD79a

positive

cyclinD1

negative

SIg

weak

FMC7

negative

 

†: fresh frozen tissue only

Scoring system for immunophenotype

 

CLL

score

other B-cell lymphoma

score

SIg

weak

1

strong

0

CD5

positive

1

negative (except mantle cell)

0

CD23

positive

1

negative

0

CD79a/CD22

weak

1

strong

0

FMC7

negative

1

positive

0

 

CLL score 4 or 5

usual score 0 to 2

Variants

Differential diagnosis

Prognosis

Incurable but indolent, with a median survival of 7 years.

References

World Health Organization Classification of Tumours, Tumours of the haematopoietic and lymphoid tissues, IARC Press 2001.

Wotherspoon AC, Hasserjian RP. Immunophenotyping in the differential diagnosis of histologically low grade B cell lymphomas Current Diagnostic Pathology 2000;6:55-63.

1EJ Schlette. B-cell prolymphocytic leukaemia. Pathology Case Reviews 2000;5 (5):274-280.