Introduction

Cutaneous horn (cornu cutaneum), is a projectile, conical, dense, hyperkeratotic nodule that resembles the horn of an animal [1]. The horn is composed of compacted keratin. A number of skin lesions can be found at the base of this keratin mound. Cutaneous horns most frequently occur in sites that are exposed to actinic radiation or burns, and hence, are typically found on upper parts of the face. Other locations include scalp, nose, eyelid, ear, lip, chest, neck and shoulder. Forearm, cartilaginous portion of the ear, leg and back of hands may also be involved [2]. Over 60% of the lesions are benign, however, malignant or premalignant lesions might be associated with it [3]. Keratosis, sebaceous molluscum, verruca, trichilemma, Bowen's disease, epidermoid carcinoma, malignant melanoma, and basal cell carcinoma have all been described in association with cutaneous horns [4]. For appropriate histopathological diagnosis, this lesion should undergo biopsy at the base of the horn for smaller lesions excision should be considered. A sex predilection has not been shown; however the possibility of harboring malignancy at the base of the lesion is increased in men when compared with age-matched women. This article describes our experience with cutaneous horns.

Patients and methods

Eleven patients with cornu cutaneum treated between January 2000 and January 2004 at the Department of Plastic and Reconstructive Surgery, Adnan Menderes University forms the basis of this report. These patients were diagnosed preoperatively based on the appearance of their lesions. After careful and detailed physical examinations all patients underwent surgical excision under local anesthesia. Defects were closed primarily if diameter was less than 2 cm, split thickness skin grafting was performed if the defects could not be closed primarily. Specimens were evaluated microscopically. Patients with malignant lesions were followed-up for minimum six months for any signs of recurrence. Data is presented as frequency.

Results

The age of the patients ranged from 45 to 67 years with a median age of 57 years. Median age was 55 years in males and 65 years in females. A male to female ratio of 3:8 was observed. All patients had history of long-term sun exposure due to farm activities and had solar keratosis on face and extremities. Three patients had past history of skin cancer (Table 1). Majority of the lesions were located on ears (4/11) (Figure 1 and 2). Three patients had a lesion on the scalp and two patients on the hand (Figure 3, and 4). One patient each had a cornu cutaneum on the lip and the buccal mucosa (Figure 5). The diagnosis of cutaneous horn was confirmed histopathologically (Figure 6). Base of the lesions were diagnosed as solar keratosis in four patients, well differentiated squamous cell carcinoma in two, actinic keratosis in two, keratoacanthoma in two, and basal cell carcinoma in one patient. One of the squamous cell carcinoma was located on ear and other on hand, while basal cell carcinoma was located on buccal mucosa. Surgical margins of the specimens were tumor free in all patients. There was no recurrence and complication in postoperative period. No adjuvant therapy given to the patients with skin cancer. Sun protection was advised to all patients.

Table 1 Patient characteristics
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Figure 1
figure 1

Cornu cutaneum on the left ear. Histologically lesion was reported as actinic keratosis.

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Figure 2
figure 2

Cornu cutaneum on the right ear histologically reported as well differentiated squamous cell carcinoma.

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Figure 3
figure 3

Cornu cutaneum due to solar keratosis of the scalp.

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Figure 4
figure 4

Cornu cutaneum on the hand due to keratoacanthoma.

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Figure 5
figure 5

Cornu cutaneum on the lip due to actinic keratosis.

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Figure 6
figure 6

Photomicrograph showing diffuse hyperkeratosis and parakeratosis consistent with cutaneous horn. (Hematoxylin & Eosin ×100).

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Discussion

Cutaneous horns, though grossly similar to horns in animals are histologically quite different from them. The animal horns are composed of superficial hyperkeratotic epidermis, dermis, and centrally positioned bone. No such axially positioned well-formed bone is observed in the gigantic human horns. On the other hand, no cystic structures lined by trichelemmal-type epithelium are seen in of the true animal horns [5]. The earliest well documented case of cornu cutaneum from London in 1588 is of Mrs. Margaret Gryffith, an elderly Welsh woman. A showman, who advertised it in a pamphlet, exhibited her for money. However, earliest observations on cutaneous horns in humans were described by the London surgeon Everard Home in 1791 [6]. Farris from Italy first described the gigantic horn in man as a well documented a case report with adequate histology [7]. A cutaneous horn (cornu cutaneum) is a protrusion from the skin consisting of cornified material organized in the shape of a horn. These horns can be derived from a variety of benign or malignant epidermal lesions. The histological appearance of the basal layer of the cutaneous horn is in the spectrum of seborrheic keratosis to infiltrated squamous cell carcinoma [1, 6]. The important issue is not the horn itself which is dead keratin, but rather the underlying condition, which may be benign (seborrheic keratosis, viral warts, histiocytoma, inverted follicular keratosis, verrucous epidermal nevus, molluscum contogiosum, etc.), premalignant (solar keratosis, arsenical keratosis, Bowen's disease) or malignant (squamous cell carcinoma, rarely, basal cell carcinoma, metastatic renal carcinoma, granular cell tumor, sebaceous carcinoma or Kaposi's sarcoma). Most commonly, they are single and arise from a seborrheic keratosis lesion [8]. Largest study of 643 cutaneous horns was reported by Yu et al [6]. According to them 39% of cutaneous horns were derived from malignant or premalignant epidermal lesions, and 61% from benign lesions. Two other larger studies on cutaneous horn too showed 23–37% of these to be associated with actinic keratosis or Bowen's disease and another 16–20% with malignant lesions [3, 9]. In the study of Bart et al [10] 44% patients had underlying malignancy. Three of their patients had past history of skin cancers [10]. Spira and Rabonovitz concluded that cutaneous horns in associated with a malignant or premalignant base is more common in patients with a past history of other malignant or premalignant lesions [11]. In our part of the country exposure to the sun is most common. Majority of the population is involved in farm activity mostly without sun protection. We believe that sun exposure is the most important etiological factor in pathogenesis of the cornu cutaneum like other skin lesions. Histopathological examination of the base of the lesion is necessary to rule out associated carcinoma, and full excision is the treatment of choice. In general, malignant or premalignant conditions are more common in older male patients, especially when the cutaneous horn is found on the face, pinna, dorsum of hands, forearms, or scalp, or when it has a larger base or base-height ratio [3]. Surgical excision remains the treatment of choice.

Conclusions

Cutaneous horns are predominantly benign lesions; however possibility of nearly one third of them harboring malignant or premalignant skin lesions should be kept in mind.