Differential Diagnosis of Pigmented Lesions in the Oral Mucosa: A Clinical Based Overview and Narrative Review Diagnosis of oral pigmentations and malignant transformations ScienceDirect 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 Figure 2 from Oral pigmentation Semantic Scholar 05 May 03 Eng