A cutaneous horn is a cone-shaped lesion on the skin that grows straight outward and looks very much like a small horn. In some cases, it is a benign growth, but in others it may be pre-cancerous or cancerous. If a cutaneous horn develops on your body, contact a doctor and have him perform a biopsy on the cells. If it's not cancerous, you don't need to do anything, though you may want to remove it for cosmetic reasons. If it's malignant, it will need to be removed as quickly as possible.