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Updated: Nov 21, 2025
A Robust Discovery Platform for the Identification of Novel Mediators of Melanoma Metastasis
Published on: March 8, 2022
The utility of PRAME staining in identifying malignant transformation of melanocytic nevi
Mary E Lohman1, Aaron J Steen2, Roy C Grekin1
1Department of Dermatology, University of California San Francisco, San Francisco, California, USA.
Background:
PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemical (IHC) staining is used to aid melanoma diagnosis. PRAME expression in nevus-associated melanoma (NAM) has not been evaluated.
Methods:
PRAME IHC was applied to cases of NAM; staining for each population of melanocytes (benign and malignant) was graded based on the percentage of labeled cells. No labeling was graded 0, 1% to 25% labeling was 1+, 26% to 50% was 2+, 51% to 75% was 3+, and >76% was 4+.
Results:
Thirty-six cases were reviewed. Sixty-seven percent (24/36) of melanomas were PRAME positive (4+) while no (0/36) nevi showed 4+ positivity. Eighty-one percent (29/36) of nevi were completely PRAME negative compared to 17% (6/36) of melanomas. In 67% of cases (24/36) PRAME differentiated between benign and malignant melanocyte populations.
Conclusions:
We identified a high rate (67%) of differential PRAME staining in adjacent benign and malignant melanocyte populations in NAM. In PRAME positive (4+) melanomas, PRAME differentiates 100% (24/24) of benign and malignant melanocyte populations. When 4+ staining is used as the threshold for positivity, PRAME staining has a sensitivity of 67% (24/36) and a specificity of 100% (36/36). These results support PRAME IHC can assist in distinguishing melanocyte populations in melanoma arising within nevi.
Insights
Preferentially expressed Antigen in MElanoma (PRAME) immunohistochemical staining can help diagnose melanoma. This study found PRAME effectively differentiates benign and malignant melanocytes in nevus-associated melanoma, showing high sensitivity and specificity.
Area of Science:
- Dermatopathology
- Immunohistochemistry
- Melanoma Diagnosis
Background:
- Preferentially expressed Antigen in MElanoma (PRAME) immunohistochemical (IHC) staining is a valuable tool for melanoma diagnosis.
- The utility of PRAME IHC in nevus-associated melanoma (NAM) has not been previously investigated.
Purpose of the Study:
- To evaluate the effectiveness of PRAME IHC in distinguishing between benign and malignant melanocyte populations within NAM.
- To determine the sensitivity and specificity of PRAME IHC for diagnosing melanoma in the context of nevi.
Main Methods:
- PRAME IHC was performed on 36 cases of NAM.
- Melanocyte populations (benign and malignant) were assessed for PRAME expression, with staining intensity graded from 0 to 4+ based on the percentage of labeled cells.
Main Results:
- 67% of melanomas exhibited strong PRAME positivity (4+), while no nevi showed 4+ staining.
- 81% of nevi were PRAME negative, compared to 17% of melanomas.
- PRAME staining differentiated between benign and malignant melanocytes in 67% of the cases reviewed.
Conclusions:
- PRAME IHC demonstrates a high rate of differential staining in adjacent benign and malignant melanocytes within NAM.
- Using a 4+ staining threshold, PRAME IHC achieved 100% differentiation between benign and malignant melanocytes in positive cases.
- PRAME IHC shows promise as an adjunct diagnostic tool for distinguishing melanocyte populations in melanoma arising in nevi, with a sensitivity of 67% and specificity of 100%.
