PRAME Expression in Recurrent/Persistent Melanocytic Nevi.

Background: Recurrent melanocytic nevi are benign melanocytic proliferations that occur after incomplete excision of a nevus. Their atypical clinical and histopathologic features complicate diagnosis, especially without knowledge of prior biopsy. The PRAME (PReferentially expressed Antigen in MElanoma) immunohistochemical stain has been increasingly used to support a diagnosis of melanoma, however, its utility in recurrent melanocytic nevi is not well established.

Methods: We analyzed PRAME expression in paired original and recurrent melanocytic nevi from 22 patients. Tissue sections underwent PRAME immunohistochemistry, evaluated by 2 dermatopathologists using 3 criteria: (1) staining intensity, (2) percentage of melanocytes with nuclear staining, and (3) a composite score.

Results: Among original nevi, 81.8% had an intensity score of 0, 9.1% scored 1, 4.5% scored 2%, and 4.5% scored 3. Percentage positivity was 81.8% at score 0 and 18.2% at score 1. All had a negative composite score. Recurrent nevi showed similar results, with 81.8% intensity score 0, 9.1% score 1, 4.5% score 2, and 4.5% score 3. Percentage positivity was 81.8% at score 0 and 18.2% at score 1, with all patients scoring negative on the composite score.

Conclusions: PRAME expression remained consistent between original and recurrent nevi, with all patients showing negative composite scores. These findings support PRAME's utility in differentiating benign recurrent nevi from melanoma, even when histologic or clinical features raise concern. PRAME staining may enhance diagnostic confidence, reducing unnecessary procedures.