Flow cytometry: Chronic Lymphocytic leukaemia

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Background to flow cytometric diagnosis

Typical CLL can be diagnosed with some confidence using flow cytometry. However, individual markers may not be expressed in all cases - particularly it may be difficult to distinguish atypical CLL from some cases of MCL or MZL.

• Atypical features should always be reported and the possibility of alternative diagnoses acknowledged.
• Cases with a low lymphocytosis (<1x10⁹) may represent monoclonal B-lymphocytosis with CLL phenotype (click here for diagnostic criteria).

Immunophenotype of CLL
CD45 expression
Typically expression of CD45 is less intense than normal T or B cells, with many cases showing variable expression with a wide spread of CD45 intensity.
Major markers useful in CLL diagnosis
Marker	Freq	Level	Comment
CD19		-	Expression is expected, but less strong than normal B cells
κ/λ			Expect weak restricted κ or λ or absent expression
CD5		-	Characteristic of CLL, usually less strong than on T cells
CD23		-	Characteristic of CLL, although can rarely be weak or absent
CD79b		wk	Expression is expected, but characteristically weak
CD200		-	Characteristically positive in CLL and negative in MCL
FMC7			May be expressed by atypical cases, generally absent
Other relevant markers
CD10		-	Infrequent in CLL, consider FL if detected
CD11C		wk	Expressed in some cases, but tends to be weak
CD20		wk	Expression is expected, but characteristically weak
CD25		wk	Expressed by many cases of CLL but characteristically weak
CD38		wk	Expressed by some cases of CLL, typically weak
CD43		-	Similar to CD200, may be helpful in some cases
CD103		-	Not expressed by CLL, consider HCL if found
CD138		-	Predominantly expressed at plasma cell differentiation

Key to table:

Key to colour code for expression frequency Click for link

Key to expression strength code and use Click for link

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