A cutaneous horn is a clinical sign rather than a specific diagnosis. Cutaneous horns are hyperkeratotic, conical projections that arise from benign, premalignant, or malignant lesions. Cutaneous horns are more commonly seen in sun-exposed areas but can occur almost anywhere on the skin, including the penis and groin. They occur more commonly in men older than 50 years.

Warts and seborrheic keratoses are common benign lesions that may be seen at the base of a cutaneous horn. Premalignant causes include actinic keratoses, and in situ or invasive squamous cell carcinoma (SCC) is reported to be found in 20% of cutaneous horns, exclusively reported in adults.

Cutaneous horns are occasionally seen in children. In this age group, they are almost always caused by warts; other reported base lesions in the pediatric age group include perforating pilomatricoma, inverted follicular keratosis, subepidermal calcified nodule, and epidermal nevus. When located on the eyelid, they are typically associated with an inflammatory lesion such as a chalazion or hordeolum. Underlying malignant lesions have not been reported in children.