PRAME immunohistochemistry is useful in the diagnosis of oral malignant melanoma.

Objectives: While the incidence of cutaneous melanoma has dramatically increased in recent years, oral malignant melanoma (OMM) remains a rare form of noncutaneous melanoma with poor survival. PRAME (PReferentially expressed Antigen in MElanoma) is reported to have diagnostic and some prognostic utility in cutaneous melanomas and some head and neck malignancies. We sought to explore the diagnostic utility of PRAME in OMM.

Methods: A total of ten specimens from eight unique cases of OMM were identified from the Oral Pathology Biopsy Service (OPBS) at University of Washington School of Dentistry between 2005 and 2019. For all cases, standard histology and immunohistochemistry stains were performed, including a stain against PRAME. The diagnoses were reviewed and confirmed by two pathologists. Clinical and epidemiologic features were described.

Results: Patient ages ranged from 55 to 82. The group consisted of five males and three females. All eight cases were located on the hard palate. Six cases represented invasive melanoma while two were early melanoma in situ. PRAME immunohistochemistry was successfully performed on seven of eight cases: six were positive (86%), one was negative (14%) and one case lacked sufficient tissue for staining.

Conclusions: Our results suggest that PRAME immunohistochemistry may be useful in the diagnosis of OMM, including early melanoma in situ. Further studies with clinical follow-up and a larger number of cases are needed to explore prognostic value as well as the ability to distinguish between benign, intermediate and malignant melanocytic proliferations of the oral cavity.