Differential Diagnosis of Pigmented Lesions in the Oral Mucosa: A Clinical Based Overview and Narrative Review 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 Black Spot on Lip: What Does It Mean? Metastatic oral malignant melanoma transformed from pre existing pigmented lesions in mandibular gingiva: Report of an unusual case ScienceDirect