Frontiers Case report: Melanosis coli combined with colon cancer, causality or coincidence? Figure 1 from Oral melanotic macule a case report. Semantic Scholar Melanosis coli: A comprehensive review Gastroenterologa y Hepatologa (English Edition) Figure 2 from Smokers' melanosis in a Nigerian population: Pigmented Lesions of the Oral Mucosa Springer Nature Link 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.