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A study of CD117 expression in dermatofibrosarcoma protuberans and cellular dermatofibroma
Sebastien Labonte1, Wedad Hanna, Bizhan Bandarchi-Chamkhaleh
1Department of Pathology, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada. seblabonte@hotmail.com
Background:
Dermatofibrosarcoma protuberans (DFSP) is a relatively uncommon spindle cell tumor of the skin. It is locally aggressive and can be a therapeutic challenge. There are case reports of partial response of DFSP to the tyrosine kinase inhibitor STI571 (Imatinib), despite the reported negativity of the tumor cells for CD117. At least one publication reported focal CD117 positivity of DFSP cells, and we would like to clarify the issue. Cellular dermatofibroma (CDF) can mimic DFSP, but typical cases are easily differentiated from DFSP by their staining pattern for CD34 and factor 13a. We also report our experience with CD117 staining of typical CDFs.
Methods:
Thirty-seven cases of clear-cut DFSP and 13 cases of clear-cut CDF were retrieved from the archives of Sunnybrook Health Sciences Center between 2000 and 2005.
Results:
All DFSPs were CD34 (+), factor 13a (-) and CD117 (-). All CDFs were factor 13a (+), CD34 (-) and CD117 (-).
Conclusions:
Our study on a relatively large number of cases confirms the negativity of DFSP and CDF for CD117. Therefore, if adjuvant therapy is attempted with drugs such as STI571 (Imatinib), the eligibility of patients should not be based on immunohistochemical assessment of CD117 expression.
Insights
Dermatofibrosarcoma protuberans (DFSP) and cellular dermatofibroma (CDF) are consistently negative for CD117. This study confirms that CD117 expression should not guide treatment decisions for these skin tumors.
Area of Science:
- Oncology
- Dermatopathology
- Immunohistochemistry
Background:
- Dermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive skin tumor.
- DFSP can be challenging to treat, with some reports suggesting response to imatinib despite CD117 negativity.
- Cellular dermatofibroma (CDF) can mimic DFSP but is typically distinguished by CD34 and factor 13a staining.
Purpose of the Study:
- To clarify CD117 expression in DFSP and CDF.
- To evaluate the utility of CD117 as a biomarker for DFSP and CDF.
- To determine if CD117 status should influence treatment decisions for DFSP.
Main Methods:
- Retrieved 37 DFSP and 13 CDF cases from 2000-2005.
- Performed immunohistochemical staining for CD34, factor 13a, and CD117.
- Analyzed staining patterns to differentiate between DFSP and CDF.
Main Results:
- All 37 DFSP cases were CD34 positive, factor 13a negative, and CD117 negative.
- All 13 CDF cases were factor 13a positive, CD34 negative, and CD117 negative.
- Confirmed consistent CD117 negativity in both DFSP and CDF.
Conclusions:
- This study confirms DFSP and CDF are CD117 negative.
- CD117 expression is not a reliable indicator for DFSP or CDF.
- Patient eligibility for therapies like imatinib should not be based on CD117 immunohistochemistry.
