This study aimed to describe the clinicopathological and treatment data of an 86-year-old, non-smoker, Caucasian female, with a solitary, asymptomatic, slowly expanding, and cylindrical growth on the lower lip, with 10+ years of evolution. She denied chronic exposure to sunlight, trauma, spontaneous bleeding, or ulceration. A clinical diagnosis of undetermined cutaneous horn (CH) was reached; an excisional biopsy was performed. The histopathological examination depicted a hyperkeratotic conical growth. At the base of the lesion, stratified squamous epithelium exhibited hyperkeratosis, spongiosis, acanthosis, and mild-to-moderate epithelial dysplasia. The definitive diagnosis was CH associated with actinic keratosis. No clinical relapses were detected after four years. Less than 25 similar cases have been published, demonstrating that CH is a relatively unusual lesion, affecting mostly sun exposed areas of middle-aged Caucasians, with no gender predilection. Excision should be the treatment of choice to diagnose the underlying lesion, since most were associated with pre-malignant/malignant diseases. This study aimed to describe the clinicopathological and treatment data of an 86-year-old, non-smoker, Caucasian female, with a solitary, asymptomatic, slowly expanding, and cylindrical growth on the lower lip, with 10+ years of evolution. She denied chronic exposure to sunlight, trauma, spontaneous bleeding, or ulceration. A clinical diagnosis of undetermined cutaneous horn (CH) was reached; an excisional biopsy was performed. The histopathological examination depicted a hyperkeratotic conical growth. At the base of the lesion, stratified squamous epithelium exhibited hyperkeratosis, spongiosis, acanthosis, and mild-to-moderate epithelial dysplasia. The definitive diagnosis was CH associated with actinic keratosis. No clinical relapses were detected after four years. Less than 25 similar cases have been published, demonstrating that CH is a relatively unusual lesion, affecting mostly sun exposed areas of middle-aged Caucasians, with no gender predilection. Excision should be the treatment of choice to diagnose the underlying lesion, since most were associated with pre-malignant/malignant diseases.