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Cutaneous (keratotic) horn (CH) is a benign, elongated, keratinous projection usually few millimetres from the skin surface.1–5 Few cases of giant CH (GCH) have been reported in English literature. We present a rare interesting case of GCH on the thumb in a woman.
A 60-year-old female farmer presented with a black projectile growth on her right thumb for last 5 years. She had undergone excision of the same lesion 3 years back with recurrence at the same site. On examination, there was a 6×1 cm long curved, blackish, elongated growth near the ulnar side of the right thumb. There was a thickened hyperpigmented lesion at the base of the growth (figure 1). A clinical diagnosis of CH was made. The growth was excised along with the base under local anaesthesia. The underlying skin defect was allowed to heal by secondary intention (figure 2). On histopathological examination (HPE), the diagnosis of CH was confirmed with features of seborrheic keratosis at the base (figure 3). The wound healed well without any recurrence 1.5 years after the operation (figure 4).
CHs (keratotic) are hyperkeratotic projections of the skin resembling the horn of an animal.6 All animal horns except those of rhinoceros contain bone cast.3 CH in human beings in contrast does not contain bone cast and is exclusively composed of compact keratin.3 The pathogenesis of the lesion has not been fully understood. The base of the CH can harbour a wide variety of histopathological findings ranging from benign, premalignant to malignant.6 The features of an invasive squamous cell carcinoma presenting as a CH are height less than the diameter of the base, painful lesion, terrace formation at the side of the lesion and base of the lesion displaying erythema.7 CH commonly occurs on the sun-exposed area or sites of chronic irritation of the body such as face, pinna, nose, forearm and dorsal aspect of forearm. A search of English literature did not reveal any case of GCH on the thumb.
The management of GCH requires wide local excision followed by careful HPE of the base.1–5 Further management depends on the underlying pathology whether benign or malignant. Long-term follow-up is required to detect any recurrence.
Giant cutaneous horn is rare on the thumb.
The possibility of cutaneous horn harbouring malignant lesion at the base is nearly one-third, which should be kept in mind.
Wide local excision with careful histopathological of the base is essential for adequate management.
MM and NKD contributed equally.
Contributors MM and NKD were involved in patient management, drafted and revised the manuscript, did acquisition and interpretation of data. RKS drafted and revised the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Obtained.
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