Giant seborrheic keratosis of the genitalia.

Genital seborrheic keratosis (SK) is a rare entity, which can be easily misdiagnosed as genital warts. Dermoscopy is a useful tool to make diagnosis of SK in such cases. We report a 50-year-old woman with a large polypoidal growth on the external genitalia. Dermoscopic examination showed fissures and ridges, cerebriform appearance, and comedo-like openings consistent with SK. The histopathology confirmed the diagnosis of SK.

Introduction

Seborrheic keratosis (SK) is common benign epidermal proliferation, which can occur anywhere in the skin the exception of palms, soles, and mucosa (there was only one report of mucosal SK in the conjunctiva).[1] SK involving the genital region is a rare entity, which can be easily misdiagnosed as genital warts. Histopathology helps in clinching the diagnosis in such cases. Recently, dermoscopy is available as a noninvasive diagnostic procedure which can be used to diagnose SK by its typical findings. We hereby report a rare and unusual case of large SK of the genitalia which initially caused a diagnostic confusion with condyloma acuminata. The diagnosis of SK in our case was established by dermoscopy and was confirmed by histopathology.

Case Report

A 50-year-old woman presented with a large polypoidal growth on the vulva of 2 years duration. The lesion started as a small pigmented patch on the right vulva, which slowly increased in size to become a large polypoidal mass and in extent to involve the entire external genitalia. There was no pain or discharge, but of late the lesion became foul smelling. There was no history of sexual promiscuity in either spouse. On physical examination, a large, pigmented, polypoidal mass (of size around 15 × 10 cm) was seen in the external genitalia involving both labia majora, labia minora, fourchette, and mons pubis [Figure 1]. Areas of reddish and whitish verrucous portions were seen within the mass. The mucosa of vagina was normal. We considered differential diagnosis of condyloma acuminata and giant SK. Dermoscopic examination was carried out, which showed fissures and ridges, cerebriform appearance, and comedo-like openings consistent with SK [Figure 2]. The histopathologic examination of a biopsy sample showed hyperkeratosis, acanthosis, and multiple horn cysts, which were also consistent with SK (acanthotic type) [Figure 3].

Figure 1

Large polypoidal mass over the entire external genitalia

Figure 2

Dermoscopic image showing fissures and ridges and comedo-like openings

Figure 3

Histopathology showing hyperkeratosis, marked acanthosis, and multiple horn cysts (hematoxylin and eosin stain, ×100)

Discussion

SKs are common benign epidermal proliferations, which present as sharply demarcated, tan to black, round or oval, elevated, “stuck on” skin lesions.[1] Classically, SK tends to increase with age.[1] The lesions are more common in the sun-exposed areas.[2] Several morphologic forms of SK are described—flat SK, pedunculated skin-tag-like, stucco keratosis, dermatosis papulosa nigra, melanoacanthoma, and inverted follicular keratosis.[13]

SK can manifest as macules, papules, or plaques.[4] Pediculated forms have also been observed in intertriginous areas.[1] Polypoidal mass (as was seen in our case) has been reported in the genital region in several case reports. Livaoglu et al.[2] and Thakur et al.[5] reported large, polypoidal SK in the genitalia in 42-year-old and 50-year-old male patients, respectively. Melanoacanthoma is a variant of SK characterized by epidermal proliferation of keratinocytes and melanocytes where the melanocytes are scattered throughout the tumor lobules rather than only in the basal layer as seen in SK.[6] Shenoy et al.[6] reported a case of melanoacathoma in the genital region. We considered the diagnosis of melanoacanthoma in our case, but ruled it was out as histopathology showed melanocytes only in the basal layer (not throughout the tumor lobule). Roth et al. reported a case of inverted follicular keratosis (a variant of SK) of the vulva.[7] Inverted follicular keratosis is considered a SK that involves the epithelium of hair follicles, that proliferates in an endophytic fashion, and that exhibits squamous differentiation in association with inflammation.[7]

The clinical diagnosis of SK may be difficult at times with only 49% accuracy in a study done by Stern et al.[4] Diagnosis becomes more difficult in the genital region as the classical clinical features of SK (distinct keratotic and follicular plugging, stuck-on appearance, etc.) disappear because of the friction and maceration typical of this area.[5] In our case, however, distinct keratotic and follicular pluggings were well discernible.

SK may be grouped into different histological subtypes: acanthotic, hyperkeratotic (also verrucous), adenoid (reticulated), plane, clonal, Bowenoid, irritated, inverted follicular keratosis, benign squamous keratosis, and melanoacanthoma.[18] Of these, the acanthotic subtype appears to be the most common. The acanthotic type, like in our case, shows marked acanthosis with predominantly basaloid cells, moderate papillomatosis and hyperkeratosis, and characteristic presence of horn cysts or pseudocysts.[1] Proliferation of melanocytes and hyperpigmentation, inflammatory lichenoid or circumscribed lymphocytic are uncommon features. Squamous eddies, as seen in irritated SK, are absent.[1]

Because the lesions of SK may not be easily diagnosable in the genital region, dermoscopy could become a handy replacement to tedious and sometimes unacceptable biopsy/histopathologic examination. The most common dermoscopic features of cutaneous SK are comedo-like openings and milia-like cysts.[19] Other features include fissures, hairpin vessels, sharp demarcation, and moth-eaten borders.[9] Comedo-like openings, that is, keratin-filled invaginations of the epidermis, are usually not seen in the vulva, due to the friction that prevents their formation in this anatomical site. Milia-like cysts, on the other hand, are histologically included in the epidermis, and therefore not eliminated by friction and maceration.[5] In our case, comedo-like openings were plentiful, but milia-like cysts were not seen. Multiple fissures (giving a cerebriform appearance) were also prominently seen in our case.

Our case highlights a rare presentation of SK as giant, polypoidal growth in the genital region and diagnostic utility of dermoscope in establishing the diagnosis.