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PRAME Immunohistochemistry in Thin Melanomas Compared to Melanocytic Nevi
Iulia Zboraș1, Loredana Ungureanu1, Simona Șenilă1
1Department of Dermatology, "Iuliu Hațieganu" University of Medicine and Pharmacy, 400006 Cluj-Napoca, Romania.
Abstract:
PRAME (PReferentially expressed Antigen in Melanoma) immunohistochemistry has proven helpful in distinguishing malignant from benign melanocytic tumors. We studied PRAME IHC expression in 46 thin melanomas and 39 melanocytic nevi, mostly dysplastic nevi. Twenty-six percent (26.09%) of the melanomas showed diffuse PRAME staining in over 76% of the tumor cells (4+), and 34.78% of the melanomas showed PRAME expression in over 51% of the tumor cells (3+ or 4+), while 8% were entirely negative for PRAME. No melanocytic nevi were PRAME 4+ or 3+. More than half of the nevi (64%) were entirely negative for PRAME staining, and 36% of the nevi showed staining expression in 1-25% (1+) or 26-50% of the cells (2+). No nevi were stained with a color intensity of 3, while 16.67% of the melanomas were stained with this color intensity. Most nevi (78.57%) were stained with an intensity of 1. With a lower positivity threshold, sensitivity increases with still reasonable specificity. The best accuracy was obtained for the 2+ positivity threshold. In conclusion, PRAME staining helps distinguish thin melanomas from dysplastic nevi. However, the threshold of positivity should be lowered in order not to miss thin melanomas.
Insights
PRAME immunohistochemistry aids in differentiating thin melanomas from benign nevi. Lowering the PRAME positivity threshold can improve detection of melanomas while maintaining specificity.
Area of Science:
- Dermatopathology
- Oncology
- Immunohistochemistry
Background:
- PRAME (PReferentially expressed Antigen in Melanoma) immunohistochemistry is a valuable tool for diagnosing melanocytic tumors.
- Distinguishing thin melanomas from benign melanocytic nevi, particularly dysplastic nevi, can be challenging.
Purpose of the Study:
- To evaluate the diagnostic utility of PRAME immunohistochemistry in differentiating thin melanomas from melanocytic nevi.
- To determine optimal PRAME expression thresholds for accurate diagnosis.
Main Methods:
- PRAME immunohistochemistry was performed on 46 thin melanomas and 39 melanocytic nevi.
- Tumor cell staining intensity and percentage were quantified.
- Diagnostic accuracy was assessed at different positivity thresholds.
Main Results:
- 26.09% of melanomas showed diffuse PRAME staining (4+), and 34.78% showed significant expression (3+ or 4+).
- No melanocytic nevi exhibited 3+ or 4+ PRAME staining; 64% were entirely negative.
- Lowering the positivity threshold increased sensitivity for melanoma detection with reasonable specificity.
Conclusions:
- PRAME immunohistochemistry effectively distinguishes thin melanomas from dysplastic nevi.
- A lower positivity threshold for PRAME staining is recommended to avoid missing thin melanomas.
