The following is a summary of “PRAME Immunohistochemical Expression and TERT Promoter Mutational Analysis as Ancillary Diagnostic Tools for Differentiating Proliferative Nodules From Melanoma Arising in Congenital Nevi,” published in the July 2023 issue of Dermatopathology by Boutko et al.

PNs are benign melanocytic proliferations that typically develop within congenital melanocytic nevi. These tumors share histological characteristics with melanoma. In diagnostically challenging cases, immunohistochemistry and genomic sequencing are frequently employed. To evaluate the utility of preferentially expressed antigen in melanoma (PRAME) immunoreactivity and telomerase reverse transcriptase (TERT) promoter mutation analysis in distinguishing congenital nevi-associated PNs from melanoma. 

PRAME immunohistochemical staining was performed on 21 PNs and 2 melanomas arising from congenital nevi. TERT promoter mutations in cases with sufficient tissue were also evaluated through sequencing investigations. In cases of PN, the positivity rates were compared to those of melanomas. Two of the twenty-one PN cases were diffusely positive for PRAME (>75 percent of tumor cells were positive). Two of the two melanomas that originated from congenital nevi were also diffusely PRAME-positive. 

Using a Fisher exact test, the difference was statistically significant. None of the malignancies contained mutations in the TERT promoter. PRAME immunohistochemical marker may help distinguish difficult-to-diagnose PNs from melanoma, but the diffuse expression is not specific to melanoma.

Source: journals.lww.com/amjdermatopathology/Abstract/2023/07000/PRAME_Immunohistochemical_Expression_and_TERT.1.aspx