Melanin pigmentation disorders of the skin and oral mucosa.

Pigmented lesions in brown, blue-black, or variations of these colors are relatively rare in the oral cavity but very common in the skin and can range from absolutely benign to highly malignant. The differential diagnosis of brown and blue-black lesions of the oral cavity includes normal racial pigmentation, melanosis, nevi, melanoma, amalgam tattoos, and disorders related to the blood or blood vessels.