Diagnostic Utility of PRAME and SOX10 Immunostaining for Vulvar Melanocytic Lesions

Vulvar melanoma (VM) is a rare type of malignant melanoma. Clinical presentations typically show mass or bleeding. Benign melanocytic lesions of the vulva include genital lentigines and genital melanocytic nevus. SOX10 is a marker commonly used in melanocytic lesions, and the preferentially expressed antigen in melanoma (PRAME) is a recent marker that shows high specificity for malignant melanoma.

The study is to evaluate the histopathology and immunohistochemistry of SOX10 and PRAME in VM and benign vulvar melanocytic lesions (genital lentigine and genital melanocytic nevus).

All cases of VM and benign vulvar melanocytic lesions were recruited. Clinical and pathological data were reviewed. SOX10 and PRAME immunohistochemistry were performed and compared between VM and benign vulvar melanocytic lesions.

Of the total nine cases with VM, 6 (66.7%) presented with mass, 2 (22.2%) had mass with bleeding, and one (11.1%) developed urinary discomfort. Histopathologically, mucosal lentiginous melanoma is the most common subtype. Thirteen cases with benign melanocytic lesions were found. In immunohistochemical studies, SOX10 showed positivity in all 9 (100%) VM and all 13 (100%) benign melanocytic lesions. PRAME showed positivity in 7 (77.8%) cases. All 13 (100%) benign melanocytic lesions show negative stains for PRAME. The sensitivity of SOX10 and PRAME in the diagnosis of VM was 100% and 88.9%, respectively. The specificity of SOX10 and PRAME in the diagnosis of VM was 0% and 100%, respectively.

SOX10 and PRAME are nuclear staining markers that can be used for diagnostic purposes and as adjunct markers for the diagnosis of VM and benign melanocytic lesions. PRAME immunostaining shows high specificity for melanoma and melanoma in situ.