Definition of melanocytic macules associated with Peutz Jeghers syndrome NCI Dictionary of Genetics Terms NCI An oral melanotic macule is a harmless dark spot found on the lip, most often the lower lip, or inside the mouth, either on the gums, inside the cheek, or on the roof of the mouth. An oral melanotic Labial Lentigo (labial melanotic macule) Cancer Therapy Advisor 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