Cutaneous Horn Arising from Angiokeratoma Associated with Underlying Dermatofibroma

Abstract

Sir, A cutaneous horn is typically a conical, hyperkeratotic projection with an appearance similar in morphology to the horn of an animal.[1 2] A large number of benign, premalignant, or malignant dermatologic conditions may underlie the cutaneous horn.[1] Only a few sporadic cases of cutaneous horn arising from angiokeratoma or dermatofibroma have been published in case reports to date. However, a cutaneous horn arising from an association between angiokeratoma and dermatofibroma has never been reported. Herein, we describe the first case of cutaneous horn due to angiokeratoma associated with underlying dermatofibroma. A 65-year-old man presented with a four year history of a hyperkeratotic lesion of 0.7 cm diameter mass on the right wrist. He reported a history of an asymptomatic brown papule at same location, which he had habitually scratched and picked at, before the development of the hyperkeratotic mass. The lesion continued to grow. His medical history was unremarkable. On physical examination, he had a firm, conical tumor projecting 0.5 cm above the skin surface [Figure 1]. A biopsy showed conical hyperkeratosis in the epidermis, papillomatosis, marked acanthosis, and multiple ectatic and thin-walled vessels in the elongated rete ridges of the papillary dermis. Interestingly, storiform cellular proliferation was also observed just below the above-mentioned lesion. Immunostainings for factor XIIIa, CD34 and D2-40 were performed, and factor XIIIa appeared consistently positive in dermal spindle cells [Figure 2a-d]. A diagnosis of cutaneous horn arising from angiokeratoma associated with underlying dermatofibroma was made. Figure 1 A 0.7-cm sized conical and hyperkeratotic lesion projecting 0.5 cm above the skin. Dermoscopic view (DermLite DL3, 10×) showing whitish structureless area (arrows) and linear looped vessel with white halo (circles) Figure 2 (a) The upper part of the separated specimen showing thick hyperkeratosis, papillomatosis, acanthosis, and thin-walled vessels (H and E, ×40), (b) the lower part showing ectatic angiomatous vessels and cellular proliferation (H and E, ×40), (c) high-power image of the tumors (H and E, ×400) and (d) diffuse positive staining in dermatofibroma (factor XIIIa, ×400) A cutaneous horn is a hyperkeratotic protrusion with a height corresponding to atleast half the diameter of its base, as in the present case.[2] Angiokeratoma, a rare cause of cutaneous horn, is a vascular malformation with ectatic blood-filled vessels in the papillary dermis, associated with slight hyperkeratosis.[1 3] Dermatofibroma, another rare cause of cutaneous horn, reveals a dermal mass composed of close whorls of fibrous tissue containing numerous spindle or histiocytic cells.[1 3] Although the exact pathophysiology of angiokeratoma remains unclear, repeated trauma is often considered important in causing a solitary angiokeratoma.[4] Ghosh et al. reported a case of cutaneous horn as a presentation of an angiokeratoma that developed from a psoriatic lesion with repeated trauma.[4] Based on histopathological findings and the patient's history, we assumed that the angiokeratoma developed on a pre-existing dermatofibroma induced by repeated irritation, even though this association might be fortuitous. The pathogenesis of cutaneous horn is not fully understood, however, aging, abundant vascularity and continuous mechanical irritation are thought to play a role in the development of the cutaneous horn.[2 4] Some author suggests that tumor cells of dermatofibromas produce factors that can both activate keratinocytes and affect their differentiation, leading to epidermal hyperplasia.[5] In the present case, all of these potential mechanisms were likely involved in the development of the cutaneous horn in a synergistic manner. In conclusion, the association of cutaneous horns with angiokeratomas and dermatofibromas is extremely rare. This report is the first example of an underlying dermatofibroma giving rise to angiokeratoma, which finally committed to the development of a cutaneous horn. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.