CD140b (PDGFRB) Expression in Atypical Fibroxanthoma/Pleomorphic Dermal Sarcoma and its Cutaneous Neoplastic Mimics

Area of Science:

• Dermatopathology
• Oncology
• Molecular diagnostics

Background:

• Atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS) are closely related cutaneous neoplasms.
• Previous studies suggest PDGFRA/B gene expression and PDGFRB immunohistochemistry as potential lineage-specific markers for PDS.
• Understanding the expression of PDGFRB in these tumors is crucial for accurate diagnosis and targeted therapy.

Purpose of the Study:

• To evaluate the diagnostic utility of CD140b (PDGFRB) protein expression in AFX, PDS, and their morphologic mimics.
• To determine the specificity and sensitivity of PDGFRB as a marker for AFX and PDS.
• To explore the implications of PDGFRB expression for therapeutic strategies in poorly differentiated cutaneous neoplasms.

Main Methods:

• Retrospective analysis of formalin-fixed, paraffin-embedded tissue sections from 18 AFX, 8 PDS, and various cutaneous neoplasms (squamous cell carcinoma, melanoma, leiomyosarcoma, rhabdomyosarcoma).
• Immunohistochemical staining for CD140b (PDGFRB) was performed and scored by extent and intensity.
• Comparison of CD140b expression patterns across different tumor types.

Main Results:

• All cases of AFX and PDS (26/26) showed diffuse CD140b positivity.
• Variable CD140b staining was observed in squamous cell carcinoma (5/26) and melanomas (16/39), including desmoplastic and spindle cell subtypes.
• Cutaneous leiomyosarcomas and pleomorphic rhabdomyosarcomas showed partial to diffuse CD140b positivity.

Conclusions:

• CD140b is a sensitive marker for atypical fibroxanthoma and pleomorphic dermal sarcoma, but its specificity is limited.
• The findings support PDGFRB as a useful diagnostic marker for AFX and PDS, aiding in differentiation from other cutaneous tumors.
• This study provides further evidence for the potential of PDGFR-targeting therapies in selected poorly differentiated cutaneous neoplasms.