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:<span style="color:navy">'''Summary'''</span>
:<span style="color:navy">'''Summary'''</span>


:CD117 is a widely expressed molecule that in haematology is used most often as a marker of primitive myeloid cells where it contributes to a diagnosis of AML. However expression is absent in around 20-30% of typical AML and there is recognised aberrant expression by up to 30% of ALL cases (more frequently in T lineage). CD117 is also expressed by mast cells, and weakly on some plasma cells
:CD200 is not lineage specific being seen in a lymphoid and myeloid disorders but has an role in diagnosis: CD200 expression aids the distinction between CLL where expression is consistent and mantle cell lymphoma (MCL) where expression is rare. It is important to realise that CD200 is not a CLL-specific marker and is also expressed on a wide range of other neoplastic B cell types


   
   
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<span style="color:navy">'''Normal expression and function'''</span>
<span style="color:navy">'''Normal expression and function'''</span>


CD117 was originally described in 1987 as c-kit (the cellular homolog of the feline sarcoma viral oncogene v-kit). Stem cell factor (SCF) binds to CD117 initiating signals that variously control apoptosis, differentiation, proliferation, chemotaxis or cellular adhesion. In myeloid cells, CD117 is expressed by early haematopoietic progenitor cells then expression is lost as the cells mature.
CD200 is a membrane glycoprotein that braodly delivers an inhibitory signal for inflammation in diverse tissues. CD200 is commonly expressed on cells of hematopoietic lineage, specifically macrophages, dendritic cells, neutrophils, mast cells and eosinophils, as well as B cells and activated T cells.  




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<span style="color:navy">'''Diagnostic role'''</span>  
<span style="color:navy">'''Diagnostic role'''</span>  


*In acute myeloid leukaemia expression of CD117 is seen in 70-80% of cases including less differentiated forms, it may be expression by any subtype, but is less likely in cases with monocytic, erythroid, or megakaryocytic maturation
*CD200 is consisently expressed in chronic lymphocytic leukemia CLL, including cases with atypical morphology or atypical expression of other surface markers
*Aberrant expression in acute lymphoid leukaemias is reported - more frequently in T-lineage ALL (particularly more primitive types). Expression in B-lineage ALL is less frequent.
*CD200 not usually expressed by MCL, making CD200 a particularly useful marker for discrimination between CLL and MCL. Note however that expression of MCL has been reported in a small number of cases so the distinction is not absolute
*Expression by mature B cell or mature T cell types is rare, although CD117 expression is described on some CD8 positive mature T cell neoplasms. *Around 30 of myeloma cases express CD117, but often expression is weak which limits its value in this disorder
*CD200 is overexpressed by many different cell types and is neither lineage nor stage-specific, being expressed by B-cell progenitors and nearly all precursor B lymphoblastic leukemias. It is expressed by over 70% of myelomas, and hairy cell leukemia also exhibits a high level of staining
*CD117 can be used to identify mast cells, but does not distinguish normal from neoplastic cells.
*expression in AML is also recorded 




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<span style="color:navy">'''Other useful information'''</span>  
<span style="color:navy">'''Other useful information'''</span>  


Outside of the haematopoietic system CD117 has a wide expression that includes germ cells, cajal cells of the gastrointestinal tract and epithelial cells in skin and breast. Gain-of-function mutations are seen in tumours affecting mast cells, myeloid cells, systemic mastocytosis, acute myeloid leukemia or cajal cells gastrointestinal stromal tumors - GOST tumours.  
CD200 is also expressed on endothelial neuronal cells and cells of the reproductive organs ovaries and placental trophoblasts.  


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|style="width: 14.25%; background: #006699; color:white"|40-80%
|style="width: 14.25%; background: #006699; color:white"|40-80%
|style="width: 14.25%; background:#66e0ff; color:black"|5-20%
|style="width: 14.25%; background: #006699; color:white"|80-100%
|style="width: 14.25%; background: #E6FAFF; color:black"|<5%
|style="width: 14.25%; background: #006699; color:white"|80-100%
|style="width: 14.25%; background:#66e0ff; color:black"|5-20%
|style="width: 12.5%; background: #E6FAFF; color:black"|<5%
|style="width: 14.25%; background: #00b8e6; color:black"|20-40%
|style="width: 14.25%; background: #00b8e6; color:black"|20-40%
|style="width: 14.25%; background: #00b8e6; color:black"|20-40%
|style="width: 14.25%; background: #00b8e6; color:black"|20-40%
|style="width: 14.25%; background: #00b8e6; color:black"|20-40%
|style="width: 14.25%; background: #006699; color:white"|80-100%
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Revision as of 15:48, 13 June 2023


Summary
CD200 is not lineage specific being seen in a lymphoid and myeloid disorders but has an role in diagnosis: CD200 expression aids the distinction between CLL where expression is consistent and mantle cell lymphoma (MCL) where expression is rare. It is important to realise that CD200 is not a CLL-specific marker and is also expressed on a wide range of other neoplastic B cell types



Normal expression and function

CD200 is a membrane glycoprotein that braodly delivers an inhibitory signal for inflammation in diverse tissues. CD200 is commonly expressed on cells of hematopoietic lineage, specifically macrophages, dendritic cells, neutrophils, mast cells and eosinophils, as well as B cells and activated T cells.



Diagnostic role

  • CD200 is consisently expressed in chronic lymphocytic leukemia CLL, including cases with atypical morphology or atypical expression of other surface markers
  • CD200 not usually expressed by MCL, making CD200 a particularly useful marker for discrimination between CLL and MCL. Note however that expression of MCL has been reported in a small number of cases so the distinction is not absolute
  • CD200 is overexpressed by many different cell types and is neither lineage nor stage-specific, being expressed by B-cell progenitors and nearly all precursor B lymphoblastic leukemias. It is expressed by over 70% of myelomas, and hairy cell leukemia also exhibits a high level of staining
  • expression in AML is also recorded


Other useful information

CD200 is also expressed on endothelial neuronal cells and cells of the reproductive organs ovaries and placental trophoblasts.

SUMMARY TABLES


Expression: primitive cell types Click (i) on table for additional information
AML B ALL Burkitt T ALL ETP ALL (i) MPAL (i) H.gones (i)
40-80% 80-100% 80-100% <5% 20-40% 20-40% 80-100%


Notes: The main application is in AML. Aberrant expression is seen in ALL particularly in T-lineage, although it may be less likely in Burkitt lymphoma. CD117 expression can indicate MPAL or ETP-ALL if other markers are consistent.


Expression: mature B cell neoplasms
CLL MCL FL MZL HCL DLBCL LPL PCL
<5% <5% <5% <5% <5% <5% <5% 20-40%

Notes: expression is uncommon in mature B-lymphoproliferative disorders, but may occur in plasma cells


Expression: mature T cell neoplasms
ATLL CTCL Sezary T-PLL T-LGL NK-LGL
limited limited limited limited limited

Notes: limited reports are consistent with expression being uncommon in T-lymphoproliferative disorders, but may occur in some cases of T-PLL

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