Oral pathology: Noting a pigmented macule that often presents a diagnostic dilemma Registered Dental Hygienists 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 Does anyone know what this black mark on my lip is? Started last August so it's I've had it nearly a year, was living in Spain at the time for 6 months Mucosal melanocytic macules