PRAME expression in dedifferentiated/undifferentiated melanomas
Erol Bayraktar
Scholar | Resident Pathology, Anatomic Pathology, Clinical Pathology, Dermatopathology
Presented at: The American Society of Dermatopathology (ASDP) Annual Meeting
Date:
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Summary: Dedifferentiated and undifferentiated melanomas (DM/UM) often do not express common melanocytic markers (S100, SOX10, Melan-A, HMB45). Diagnosis clues include differentiated tumor focus, prior melanoma history, unusual tumor sites, melanoma-type spread, melanoma-compatible mutations, or lack of another primary tumor. Immunohistochemistry for PRAME was assessed by semi-quantitative method evaluating intensity and percentage positivity.
PRAME staining: 7 cases (64%) showed diffuse nuclear expression, 3 cases (27%) strong nuclear staining, 1 case (9%) no expression. No PRAME expression in atypical fibroxanthomas (AFX) or undifferentiated pleomorphic sarcomas (UPS), which are mimickers of DM/UM.