Objective: Oral melanocytic nevi (OMN) are histologically similar to skin nevi; however, they are much rarer and not always related to sun exposure. This study aimed to characterize the histopathological, immunohistochemical, and molecular features of OMN in sun-exposed (vermilion lip) and sun-protected (intraoral) regions.
Method: Cross-sectional study on 14 intraoral and 20 vermilion lip OMN. Hematoxylin-eosin, immunohistochemistry for TRP2 and MiTF, and RT-qPCR for TRP2 and MiTF were used to assess histopathology, protein, and mRNA expression, respectively. Statistical analysis was performed.
Results: Intramucous and blue nevi are the most frequent histological subtypes. Intraoral lesions predominantly affect Brown or Black individuals (64.3%), presenting mostly as macules. Vermilion lip nevi affect White individuals (75%), with elevated lesions (30%). Histologically, intraoral nevi show asymmetric, lack theques formation and floret cells, and present no mitotic activity or pleomorphism, while vermilion nevi display pleomorphism, symmetry, theques formation, floret cells, and solar elastosis. TRP2 and MiTF protein and mRNA expression were upregulated in both groups (p < 0.05), with no differences between them (p > 0.05).
Conclusions: Intraoral and vermilion lip nevi have distinct histopathological features, but similar TRP2 and MiTF protein and mRNA expression. This characterization may aid the histopathological diagnosis of OMN and distinction from other oral pigmentations.
Keywords: MiTF protein; TRP2 protein; mouth; oral nevus.
© 2025 The Author(s). Oral Diseases published by John Wiley & Sons Ltd.