Oral Melanocytic Nevi and Malignant Melanoma

Melanocytic Lesions

• Palate and gingiva are favored sites for oral melanocytic lesions.
• Histologically, a cluster of naevus cells is seen below the epithelium.

Malignant Melanoma

• Malignant melanoma is a neoplasm of melanocytic origin, with most cases occurring on the skin.
• Incidence of malignant melanoma increases with age, reaching a peak between 80 and 84 years.
• Oral malignant melanoma occurs much less frequently than its cutaneous counterpart.
• Ultraviolet light exposure, fair complexion, and sun sensitivity cause cutaneous melanoma, but no aetiological factors are known for mucosal melanoma.
• Malignant melanomas may develop denovo or from a preexisting benign melanocytic lesion.

Clinical-Pathologic Features of Malignant Melanoma

• The most frequent sites are the palate and upper alveolar ridge.
• Early oral melanomas are asymptomatic dark brown or black flat patches.
• Symptoms only develop in the late stages with nodular growth, pain, ulceration, bleeding, or loosening of teeth.
• Melanomas grow in a predictable fashion, initially spreading laterally within the epithelium, and later extending into the connective tissue.

Oral Melanoacanthoma

• Oral melanoacanthoma typically presents as a diffuse, rapidly enlarging area of macular pigmentation.
• Histologically, it is characterized by spongiotic epithelium containing dendritic pigmented melanocytes throughout the lesional epithelium.
• The pathophysiologic mechanism is most consistently associated with acute regional trauma or chronic irritation.

Patient Management

• A biopsy is necessary to confirm the diagnosis of oral melanocytic nevi and to rule out malignant melanoma.
• Treatment of oral melanoacanthoma is typically not indicated after diagnosis has been established.

Melanocytic Nevus

• Melanocytic nevi, commonly referred to as “moles,” represent a group of benign tumors that develop due to melanocytic growth and proliferation.
• In general, melanocytic nevi are acquired lesions with both environmental and genetic factors thought to play a role in their development.

Clinical-Pathologic Features of Melanocytic Nevus

• Intraoral lesions are unusual and form circumscribed brown to black patches, usually flat, approximately 5 or 6 mm across.
• Oral/labial melanotic macules are present in up to 3% of the population, are typically observed in patients in the fourth and fifth decades, and have a 2:1 female predilection.

Oral/Labial Melanotic Macules

• Oral/labial melanotic macules are solitary, well-circumscribed lesions that are typically less than 1 cm in diameter.
• They may appear on any surface but are most commonly observed on the buccal mucosa, gingiva, and palate.
• Histopathological analysis reveals an increase in melanin in the basal and parabasal layers of normal stratified squamous epithelium without an increase in the number of melanocytes.

Patient Management of Oral/Labial Melanotic Macules

• Oral/labial melanotic macules are considered benign lesions without malignant potential.
• Since early malignant melanoma may have a similar clinical appearance, it is strongly advisable to perform an excisional biopsy for any suspected macules.