The utility of PRAME immunohistochemistry in the evaluation of challenging melanocytic tumors.

Background: PRAME (PReferentially expressed Antigen in Melanoma) immunohistochemistry has demonstrated high specificity for unequivocal melanomas; however, its utility in ambiguous melanocytic neoplasms has yet to be fully elucidated.

Methods: Cases of challenging melanocytic neoplasms were subclassified into one of three categories: challenging, favor benign (FB), challenging, cannot be subclassified (CCS), or challenging, favor malignant (FM). Using a previously published system, whereby cases with diffuse staining (>75%) were considered positive, scoring of PRAME was performed.