A Guide to Clinical Differential Diagnosis of Oral Mucosal Lesions Not Cancer! Understanding Dark Spots in the Mouth, Have you noticed a dark spot on your lips, gums, or inside your mouth? Dont panic! In this video, Dr. Shifali Arora explains melanotic macules a Oral Mucosal Melanosis IntechOpen 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.