Metastatic oral malignant melanoma transformed from pre existing pigmented lesions in mandibular gingiva: Report of an unusual case ScienceDirect Figure 1 from Oral melanotic macule a case report. Semantic Scholar Nevi and Malignant Melanoma Plastic Surgery KeyPlastic Surgery Key Brown spots, especially on the lips, can be alarming to some. In some instances it can indicate rare oral mucosal melanoma, however in this case it was a non cancerous labial melanotic macule.