Melanocytic nevi of the oral mucosa are benign tumors of melanocytes, the pigment-producing cells in the skin and juxtacutaneous mucous membranes, including the oral mucosa. Melanocytic nevi are much less common in the oral mucosa than on the skin (Buchner and Hansen 1987; Buchner et al. 2004; Müller 2010). The intramucosal nevus is the oral counterpart of the cutaneous dermal nevus.
In an intramucosal or subepithelial nevus, the (nests of) nevus cells are located within the underlying connective tissue and are often nonpigmented. They are usually small, 4–6 mm in greatest diameter, well-circumscribed macules or slightly raised papules.
Intramucosal nevi are the most common subtype (60–80%) of nevi.
The age ranges from 3 to 87 years with a mean age for intramucosal nevi of 38 years.
A female preference has been reported (female to male ratio 1.5:1).
The hard palate, buccal mucosa, and gingiva are the most common locations.
No treatment is required for nevi. However, most adult-onset pigmented lesions are removed to rule out malignancy (malignant melanoma).
After excision neither recurrences nor malignant transformation has been reported (Meleti et al. 2007).
No immunohistochemical stains are necessary for diagnosing an oral melanocytic nevus. However, nevus cells are positive for S100 and HMB-45 (Gazit and Daniels 1994).
Cutaneous melanocytes frequently harbor oncogenic BRAF or less commonly NRAS or HRAS mutations. However, no molecular studies have been reported on oral melanocytic nevi.