Snake plant-like morphology of a cutaneous horn: An unusual presentation

A 47-year-old female presented with a 10-year history of a yellowish raised lesion over her upper lip, allegedly developing after self-manipulation of a mole-like lesion. Radiofrequency ablation was done 5 years ago, but the lesion recurred a few months later. She was otherwise healthy, with no known comorbidities. On examination, multiple clustered, curved, yellowish hard projections were seen arising from a firm base over the right side of her upper lip, surrounded by a collarette of skin [Figure 1]. The lesion’s age and clinical characteristics, including a narrow base with a significantly greater height, surface ridges, and the absence of significant tenderness and erythema, were suggestive of cutaneous horn overlying a benign lesion. Histopathological examination of the excised lesion revealed features of cutaneous horn, along with acanthosis, hypergranulosis with coarse keratohyaline granules, and vacuolated superficial keratinocytes, suggestive of verruca vulgaris [Figure 2]. There were no signs of recurrence at 1-year follow-up.

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Figure 1:

Multiple closely clustered, curved, yellowish hard projections of different lengths, arising from of base surrounded by a collarette of skin, over the upper lip.

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Figure 2:

Massive compact hyperkeratosis with orthokeratosis and parakeratosis, acanthosis, hypergranulosis with coarse keratohyaline granules, and vacuolated superficial keratinocytes (a): hematoxylin and eosin (H&E) ×10; (b): H&E ×40.

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A cutaneous horn or cornu cutaneum is a hyperkeratotic, exophytic projection arising from the stratum corneum layer of the skin, with its height exceeding half the width of the base. It is the product of a reactive process driven by certain intrinsic and extrinsic factors occurring in certain benign, premalignant, or malignant skin lesions. The abnormal keratinization results in the formation of a densely compacted keratinous structure resembling an animal horn. It is typically seen over sun-exposed sites such as the face, scalp, neck, dorsum of hands, and forearms, with sizes ranging from a few millimeters to several centimeters. Histopathological examination reveals pronounced hyperkeratosis, with orthokeratosis and parakeratosis. Although the diagnosis is primarily clinical, a biopsy of the base is essential to identify the underlying skin lesion. Therefore, complete surgical excision followed by appropriate management of the underlying lesion remains the treatment of choice.