Test

Background

Typical CLL can be diagnosed with some confidence using flow cytometry. However, atypical cases are regularly encoutered and can cause diagnosic difficulty.

This image shows a typical CLL cells and a dot plot of CD45/SSc. Note that although the CLL cells (shown in blue) generally lie close to the position of normal lymphocytes, consistent with their "anergic nature": CLL cells express low levels of B-cell receptor associated molecules (e.g. CD19, CD79B and sIg) and also will generally have lower expression of CD45 than typical T cells (shown in red) or NK cells (shown in green). CLL often has a wide range of CD45 expression causing the population to have a "sausage like" shape on a CD45/SSc plot.

file CLL image file CD45CLL.jpg left 250px

Immunophenotype of CLL
Major markers useful in CLL diagnosis
Light chains	Wk	Either weak resticted κ or λ or undetectable expression
CD19	Wk/mod	Expression is expected, but less strong than normal B cells
CD20	Wk	Expression is expected, but characteristically weak
CD79A	Wk	Expression is expected, but characteristically weak
FMC7	Wk	May be expressed by atypical cases, generally absent
Other markers with diagnostic relevance

Immunophenotype:

Markers of B-lineage

• Immunoglobulin light chains: expect either light chain restriction with low intensity, or undetectable expression
• CD19 should be detected, but intensity is generally weak in CLL
• CD20 has expected expression in CLL, but intensity is generally weak
• CD79b expression is characteristically weak in CLL

Markers allowing diagnostic distinction

• FMC7 will have low or absent expression, high expression is particularly may suggest alternative disorders such as MCL or MZL
• CD5 should be expressed at moderate intensity in CLL (note also on expressed on mcl and occasionally on other lpd)
• CD23 has expected expression in CLL often at low intensity, generally absent in mcl but variably present on other lpd
• CD200 expressed on most CLL cases as well as other b-lpd but is most frequently absent in mcl optional markers extended panel for atypical cases
• CD43 a pan b-cell marker with expected expression in CLL; frequently but not always absent in mcl

Pitfalls