Cutaneous horn masquerading as a seborrheic keratosis.

PURPOSE: To report a case of seborrheic keratosis of the inner canthus presenting as cutaneous horn. OBSERVATION: A 67-year-old Asian male presented with a rod-shaped, pedunculated mass on his inner canthus. The mass grew rapidly and within 2 months measured 3.0 cm in length and 0.5 cm in diameter. It was completely excised and submitted for microscopic examination. The specimen consisted of a proliferation of basaloid cells arranged in a papillary pattern and associated with significant hyperkeratosis and parakeratosis of the overlying squamous epithelium. The pathological diagnosis was reported as seborrheic keratosis from the skin of the inner canthus. CONCLUSIONS AND IMPORTANCE: Seborrheic keratosis can develop into a rapidly expanding lesion such as a cutaneous horn and can be found in unusual locations. To our knowledge, this is the first report of a seborrheic keratosis from the skin of the inner canthus.

Introduction

Seborrheic keratosis is a common skin neoplasm and accounts for about 20% of benign tumors of the eyelid, secondary in frequency only to squamous papilloma.1, 2 This common benign epithelial neoplasm is seen mostly on the eyelids and faces of persons of middle-to advanced age, but other common locations include the chest, back, and abdomen. Although seborrheic keratosis is not unusual in several areas of the skin, the occurrence of this benign epithelial neoplasm on the inner canthus is very rare. There have been some case reports of other lesions involving the inner canthus, such as lymphoid follicles and hemangiopericytomas – all of these cases were treated by complete excision.4, 5 Lesions of seborrheic keratosis are typically sharply demarcated, slightly elevated brown macules with a “stuck-on” appearance, and rarely present as a cutaneous horn (cornu cutaneum), which is a morphological designation for a protuberant mass of keratin that resembles the horn of an animal. To our knowledge, our case of seborrheic keratosis located on the inner canthus presenting as a cutaneous horn is the first to be reported.

Case report

In November of 2014, a 67-year-old Asian man was referred to the Department of Ophthalmology for diagnosis and treatment of a rod-shaped, pedunculated mass arising from the skin of the inner canthus. He gave a history of this mass being present for two months and displaying rapid growth. There was no pain or other discomfort noted. The patient appeared well and healthy and had no remarkable medical history. He denied any prior cutaneous or systemic malignancies and had no obvious weight loss or any other signs of illness. On physical examination, no abnormity was noted of the heart, lungs or abdomen.

The spindle-shaped mass measured 3.0 cm in length was dark yellow in color and with a smooth surface. The base of the lesion was soft and pliable and could be twisted easily, but the periphery was stiff. Routine blood, urine and stool screening tests were unremarkable. Chest radiography, electrocardiogram and routine coagulation tests showed no abnormities as well.

A complete excision of the mass from the area of the inner canthus was performed. The base of the lesion was found to have invaded deep into the subcutaneous tissues, but it did not extend to the medial canthal ligament (Fig. 1. A). The base of the lesion lacked clear boundaries, but there was no adherence to the surrounding tissues, and no encapsulation was noted. The flesh-like base demonstrated blood vessels. Following excision, the specimen was measured as 0.5 cm in diameter (Fig. 1. B). Sutures from the operative site were removed after five days.

Fig. 1

The gross morphologic characteristics of the eyelid mass. (A) Photograph showing a rodlike palpebral mass poking outward from the left inner canthus region. The mass was faint yellow with a smooth surface and longitudinal texture. The root of the mass was with good mobility, could be twist easily, but the other part of mass was stiff. (B) After complete removal of the mass, the size was measured as 0.5 cm in diameter and 3.0 cm in length. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

The microscopic diagnosis was reported as seborrheic keratosis consistent with the presence of a papillary proliferation of basaloid cells with hyperkeratosis and parakeratosis of the surface squamous epithelium (Fig. 2). No further recurrence has been noted during the two-month follow-up, and the wound healed without complications.

Fig. 2

The pathological characteristics of the section. Papillary proliferation of basaloid cells with hyperkeratosis and parakeratosis in the squamous epithelium. Magnification of A, B and C: 4 × , 10 × and 20 × respectively. A high-resolution version of Fig. 2B for use with the Virtual Microscope is available as eSlide: VM02603

Discussion

Seborrheic keratosis is a benign epithelial neoplasm that occurs mainly on the skin of the eyelids and face of individuals between 40 and 50 years of age. However, seborrheic keratosis is rarely seen on the inner canthus. To date, our case is the first case of seborrheic keratosis located on the skin of the inner canthus to be reported in the medical literature.

The peculiar morphology of this lesion, however, also demonstrates some of the characteristics of cutaneous horn. The essential concern in these cases is not the horn itself, but rather the nature of the underlying tissue producing the horn. To make a definite diagnosis, a complete excision of the lesion and a microscopic exam becomes very important.

The differential diagnosis of cutaneous horn includes squamous cell papilloma and other lesions such as basal cell carcinoma, keratoacanthoma, inverted follicular keratosis, and actinic keratosis. The pathologic diagnosis submitted with this case strongly supports the premise that this is in fact, a benign lesion. In addition, there have been no signs of systemic malignancies according to physical examinations However, considering its rapid growth rate within a two-month period, careful follow-up is required to further rule out the possibility of underlying malignancy.

There are several sub-types of seborrheic keratosis that show histologic and sometimes clinically distinct variations from what is referred to as common seborrheic keratosis. These groups include reticulated seborrheic keratosis, stucco keratosis, clonal seborrheic keratosis, irritated seborrheic keratosis, seborrheic keratosis with squamous atypia, melanoacanthoma, and dermatosis papulose nigra. The pathological examination in our case reveals a papillary proliferation of basaloid cells with hyperkeratosis and parakeratosis of the squamous epithelium, and its somewhat deep invasion component is suggestive of inverted follicular keratosis. In conclusion, this case shares some characteristics of common seborrheic keratosis and some of its variants and is particularly uncharacteristic in its gross appearance as well as its rapid growth behavior.

Conclusion

Seborrheic keratosis can occur on the inner canthus, although it is rare and has not been previously described in the literature. It can also display other unusual features such as cutaneous horn, as in our case. Furthermore, efforts should be made to understand the unusual presentation of this rare case of seborrheic keratosis because adequate awareness will benefit its pre- and intraoperative management.

Patient consent

The Review Board at our institution stated that no approval is required for this study. All patient information was in compliance with the policies at Xiangya Hospital. Written patient consent for publication was obtained during the clinical follow-up.

Conflict of interest

We have no conflict of interest to disclose.