Abstract

Background: Preferentially expressed antigen in melanoma (PRAME) immunohistochemistry is useful for the differentiation of malignant and benign melanocytic proliferations. However, its diagnostic role has not been thoroughly evaluated in acral melanocytic tumors. Objective: To evaluate the utility of PRAME immunohistochemistry for the diagnosis of acral melanocytic tumors compared with other potential markers including c-Kit, c-Myc, and cyclin D1. Method: Melanocytic tumors were classified into acral nevi, challenging melanocytic tumor (superficial atypical melanocytic proliferation of uncertain significance (SAMPUS)-favor benign (SAMPUS-FB), SAMPUS-favor malignant (SAMPUS-FM)) and acral melanoma. The expression level of each antibody and their diagnostic performance were assessed. Results: A total of 106 cases of acral nevus (n = 32), SAMPUS-FB (n = 17), SAMPUS-FM (n = 20), and acral melanoma (n = 37) were included. The diagnostic power assessed by area under the receiver operating characteristic curve (AUC) for distinguishing acral melanoma and acral nevus was highest for PRAME (AUC = 0.997), followed by c-Myc (AUC = 0.755), cyclin D1 (AUC = 0.652), and c-Kit (AUC = 0.573). At PRAME expression level ? 30% as a positive test for acral melanoma, the sensitivity and specificity of PRMAE for discriminating acral melanoma from acral nevus were 100.0% and 96.9%, respectively. PRAME immunohistochemistry also discriminated SAMPUS-FM from SAMPUS-FB with sensitivity and specificity of 90.0% and 76.5%, respectively. Conclusions: PRAME immunohistochemistry using cutoff value of 30% can effectively be used to distinguish various spectrum of acral melanocytic neoplasms.

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