Conjunctival Nevus: Symptoms, Causes and Treatment Melanoma Pictures: Skin Changes and What to Look For 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 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 How Can You Tell if It's Melanoma or Just a Mole? Melanocytic Nevi MD Searchlight