Giant cutaneous horn with naevus sebaceus

Cutaneous horn (cornu cutaneum) is the clinical description of a hyperproliferation of compact keratin in response to a wide array of underlying benign and malignant pathologic changes. A cutaneous horn more than 1 cm in height is rare, because surgeons remove these horns early. Four main features are associated with a premalignant or malignant histopathological change at the base of a cutaneous horn: patient age, sex, site, and geometry of the lesion. The mean age of patients whose cutaneous horns showed a premalignant or malignant base pathology was 8.9 years older than the mean age of patients in whom the base pathology was benign. Men are more likely to develop a cutaneous horn with a premalignant or malignant base pathology. More than 70% of all premalignant or malignant lesions are found on the nose, pinnae, back of hands, scalp, forearms, and the face, and a cutaneous horn found at these sites is 2:1 times more likely to have been derived from a premalignant or malignant base than from any other part of the body. Lesions with a wide base or a low height-to-base ratio were markedly more likely to show a premalignant or malignant base pathology. Cornu cutaneum refers to a reaction pattern rather than a specific lesion. Different types of skin lesions underlie cutaneous horns such as keratoses, sebaceous molluscum, verruca, trichilemma, Bowen's disease, epidermoid carcinoma, malignant melanoma, and basal cell carcinoma.