Black Spots on Teeth & Gums Stains or Something Serious? Brown spots, especially on the lips, can be alarming to some. In some instances it can indicate rare oral mucosal melanoma, however in this case it was a non cancerous labial melanotic macule. Common oral mucosal lesions Den norske tannlegeforenings Tidende Pigmented (Purple or Brown) Lesions in the Mouth Pigmented (Purple or Brown) Lesions in the Mouth Kazemi Oral Surgery Facialart.com