The Expression of PRAME as an Aid for Diagnosis and Evaluation of Histologic Margins of Intraepidermal Cutaneous Melanoma in Xeroderma Pigmentosum Patients.

Xeroderma Pigmentosum (XP) is a genetic disorder characterized by photosensitivity, dyschromia, and high risk of skin cancer. From a clinical and histologic view, it can be difficult to diagnose cutaneous melanoma (CM) in XP patients and to define its resection margins. We aimed to study the role of PRAME (PReferentially Expressed Antigen in MElanoma) in differentiating intraepidermal CM from superficial atypical melanocytic proliferation of uncertain significance (SAMPUS) and evaluating the histological margins of CMs. We included XP patients. melanocitic and nonmelanocytic lesions with adjacent skin, and, as control groups, sun-damaged skin from non-XP individuals. Melanocytic lesions with a consensus diagnosis were grouped into CM, SAMPUS, or benign. The selected samples were PRAME-immunoshistochemically stained, and the ratio between immuno-positive cells/mm was recorded, according to Olds and colleagues for intraepidermal lesions. Lezcano and colleagues' method was used for intradermal lesions. Clinical data from XP patients were reviewed. All 9 patients were alive and well at the study closure, even those who developed melanoma metastases. Positive/diffuse PRAME expression was found in 29% (7/24) of intraepidermal CMs and 20% (1/5) SAMPUS samples. All 103 XP control samples and 24 adjacent lesions skin of non-XP patients were PRAME negative. This was a single-center and retrospective study, using a relatively small sample, limiting our conclusions. In XP patients' lesions, PRAME expression could help in the setting of challenging melanocytic tumors and surgical margins evaluation. It is also possible that the method can avoid overdiagnosis and, consequently, more aggressive treatment recommendation in unequivocal CM cases.