Oral melanotic macula on the lower labial vestibular mucosa on a Download Scientific Diagram What Is Melanonychia? What Causes It and How It's Treated Melanotic macule. Benign. Dark spot on labia (or lip). Analogous to lentigo simplex. Hyperpigmented basal keratinocytes & dermal melanophages. Slight in single basal melanocytes; NO nests. More info like this in Definition of melanocyte NCI Dictionary of Cancer Terms NCI Oral Mucosal Melanosis IntechOpen Melanoma Skin Cancer