Publication date: Jan 12, 2021
PRAME (PReferentially expressed Antigen in MElanoma) immunohistochemical (IHC) staining is used to aid melanoma diagnosis. PRAME expression in nevus associated melanoma (NAM) has not been evaluated.
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, 1-25% labeling was 1+, 26-50% was 2+, 51-75% was 3+, and?>?76% was 4?+?.
36 cases were reviewed. 67% (24/36) of melanomas were PRAME positive (4+) while no (0/36) nevi showed 4+ positivity. 81% (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.
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 ICH can assist in distinguishing melanocyte populations in melanoma arising within nevi. This article is protected by copyright. All rights reserved.