Melanocytic nevi and melanoma: unraveling a complex relationship Oncogene Oncology Letters Non Melanoma Skin Cancer 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. Epithelial, non melanocytic and melanocytic proliferations of the ocular surface ScienceDirect