An Innocent Giant

Abstract

A cutaneous horn (cornu cutaneum) is a protrusion from the skin composed of a cornified material. It may be associated with a benign, premalignant, or malignant lesion at the base, masking numerous dermatoses. In a 24-year-old female, a giant cutaneous horn arising from a seborrheic keratosis located on the leg is presented. This case has been reported to emphasize that a giant cutaneous horn may also occur in young patients, even in photoprotected areas, and are not always associated with malignancy.

Introduction

What was known?

1. Cutaneous horns with underlying malignancy are more commonly associated with male sex, higher age, photoexposed areas, and a wide base or a low height to base ratio.

2. Giant cutaneous horns are usually associated with malignancy.

Cutaneous horn (cornu cutaneum) is a chronic, dense, conical, hyperkeratotic cutaneous protuberant mass usually affecting the head and neck region. It is regarded as a reactive phenomenon to the underlying pathology that is usually benign. However, a premalignant or malignant lesion may be associated with or without actinic damage as the underlying pathology.[1] Most cutaneous horns do not project more than 1 cm from the skin surface and are usually shed off due to trauma or are excised before they grow further. Large cutaneous horns or giant horns are rarely encountered and are more commonly associated with malignant pathology. The present case is one of the biggest cutaneous horns recorded in literature. Occurrence of such a gigantic cutaneous horn in the present case reflects lack of awareness and gross personal neglect by the patient. It highlights the fact that giant cutaneous horns may not always be associated with malignancy, especially when they are growing slowly over a period of time.

Case History

A 24-year-old female, manual labourer presented with a dark-colored, woody-hard growth over her left leg since two years. The lesion had started growing as a small nodule arising over an itchy hyperpigmented plaque, which gradually enlarged to form a large horny mass. There was a history of occasional pain and oozing over and around the lesion since 3 months. There was no history of similar lesion anywhere else on body. On examination, there was a single brownish-black, curved, woody-hard hyperkeratotic growth of size 9.5 × 6 cm along with areas of hemorrhagic crust and ulceration [Figure 1] arising over a lichenified plaque on the medial aspect of the left leg. On palpation, the base was slightly tender and indurated. There were few lichenified plaques of variable sizes along with a few areas of depigmentation over the surrounding skin. There was no regional lymphadenopathy. A differential diagnosis of cutaneous horn with either an underlying lichen simplex chronicus or squamous cell carcinoma or verrucous carcinoma was made. Excision biopsy was done along with 5 mm margins, followed by healing of the defect with secondary intention in the following 6 weeks.

Figure 1.

Hyperkeratotic horny lesion on the medial aspect of the left leg

Histopathological examination showed an exophytic as well as an endophytic proliferation of epidermis with exuberant hyperkeratosis, acanthosis, and papillomatosis along with numerous squamous eddies composed of eosinophilic flattened cells arranged in a concentric fashion. No cellular or nuclear atypia was seen. The upper dermis showed moderate mixed inflammatory cell infiltrate composed of lymphocytes, plasma cells, and eosinophils. The features were suggestive of a cutaneous horn overlying a seborrheic keratosis [Figure 2].

Figure 2.

(a) Photomicrograph showing proliferation of epidermis with hyperkeratosis, acanthosis, and papillomatosis along with numerous squamous eddies (H and E, ×40). (b) Photomicrograph showing squamous eddy (H and E, ×400)

Discussion

A cutaneous horn is a morphologic designation referring to cohesive keratinized material protruding above the surface of the skin.[1] Although it derives its name from its semblance to animal horn, it lacks an axially positioned, well-formed bone characteristic of an animal horn.[2]

Pathogenesis of horn formation in humans has not been fully elucidated, but it has been suggested to be because of abnormal accumulation, excessive adhesiveness, and compaction of keratin. Various underlying dermatoses associated with cutaneous horn include seborrheic keratoses, wart, nevus sebaceous, molluscum contagiosum, rhinosporidiosis, psoriasis, lichen planus, porokeratosis, actinic keratosis, histiocytoma, follicular infundibular tumor, keratoacanthoma, basal cell carcinoma, squamous cell carcinoma, and so forth.[3] However, the predisposing factors that lead to the formation of a horn in these dermatoses is not known. In a large study by Yu et al., out of 643 cases of cutaneous horn studied, 61.1% had benign base pathology whereas 38.9% had premalignant or frankly malignant base pathology. Among benign pathology, seborrhoeic keratosis was the most common underlying lesion.[4]

Horns overlying a malignant pathology do not differ clinically from those having a benign underlying pathology although they are more commonly associated with male sex, older age, photoexposed areas, and giant horns characterized by a wide base or a low height to base ratio.[4] Because of the risk of presence of an underlying malignant condition, deep biopsies or total excision of small lesions are recommended.[1,5]

Cutaneous horns in humans do not grow more than 1 cm in height as these lack a bony skeleton characteristic of animal horns.[2] Giant human horns are large cutaneous horns that can achieve enormous sizes that can be even up to 25 cm in some cases.[6] Although giant cutaneous horn is more common with malignant pathology, a few cases have previously been reported with benign cutaneous pathologies such as verrucae vulgaris,[2] xeroderma pigmentosus,[3] burn scar,[7] and naevus sebaceous,[8] and only once reported in seborrheic keratosis.[9]

What is new?

1. Giant cutaneous horn may occcur in younger patients even on photoprotected areas.

2. Giant cutaneous horn not always is associated with malignancy, especially when they are slow growing over a period of time.