Pigmented Oral Lesions: Clues to Identifying the Potentially Malignant Consultant360 ORAL MELANOTIC MACULE (OMM) (Also called focal melanosis labial melanotic macule) A benign, localized, flat pigmented lesion of the oral mucosa Caused by a focal increase in melanin production 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. Pigmented Lesions of the Oral Mucosa Pocket Dentistry