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Typical HCL morphology, cells are medium size, with a partly activated chromatin pattern and oval or indented nuclear shape, the cytoplasm is typically blue/grey with irregular and fine projections (hairs)

Background to flow cytometric diagnosis

HCL expresses typical and unusual markers that together with morphology can allow diagnosed with some confidence using flow cytometry.

However, no marker is unique to HCL and unusual marker patterns can lead to diagnostic difficulty. If this is the case then the atypical features should be reported, since histopathology and molecular testing can each be used to further evaluate these cases.

CD45 expression

Immunophenotype
Major markers useful in diagnosis
Marker	Freq	Level	Comment
κ/λ		Stg	Expect strong restricted expression of κ or λ
CD19		-	Expression is expected and may be strong in HCL
CD11C		Stg	Strong expression of CD11c is typical of HCL
CD25		wk	A typical and most frequently strongly expressed marker
FMC7		Stg	Typically this marker is strongly expressed
CD103		-	A characteristic marker of HCL with good specificity
Other useful markers
CD5		-	Infrequent but reported in some cases
CD10		-	Infrequently expressed in typical HCL
CD20		Stg	Expression is expected, and typically strong
CD23		-	Expression of CD23 is infrequent in HCL
CD38		wk	Not typically expressed by HCL, may be seen
CD43		-	Tends to be expressed at relatively high intensity
CD79b		wk	Expression is expected
CD138		-	Predominantly by cells with plasma cell differentiation
CD200		-	Characteristically positive in HCL and often strong

Key to table:

Markers most useful in initial diagnosis are underlined in blue text

Key to colour code for expression frequency Click for link

Key to expression strength code and use Click for link

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