An Adenoid Type of Giant Seborrheic Keratosis of the Genitalia

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Seborrheic keratosis (SK), also known as senile warts or basal cell papilloma, is a benign skin tumour, which presents as a well-circumscribed pigmented round papule or plaque with a ‘stuck on’ appearance.^[1] Their incidence increases with age and they are commonly found on sun-exposed locations except palms and soles.^[2]

A 60-year-old man presented with a single large painless verrucous lesion in the groin of 2 years duration. The lesion started as a small, pigmented papule which slowly increased in size to become a verrucous mass. Past medical history and family history were unremarkable. On examination, a large verrucous well-defined nodular plaque of size 8 × 4 cm was present in the right medial inguinal region. The lesion had a polypoidal, irregular and verrucous surface. There was no discharge or bleeding on manipulation [Figure 1]. Regional lymph nodes were not enlarged. The rest of the mucocutaneous examination was within the normal limits. Systemic examination was normal. Histopathological examination revealed hyperkeratosis, papillomatosis, follicular plugging and acanthosis. Thin proliferating strands of basaloid cells arising from the epidermis with interdigitation were seen. The superficial dermis showed oedema and pigmentation with melanophages [Figure 2]. Serology for hepatitis and human immunodeficiency virus were non-reactive. Based on the clinical and histopathological findings, a diagnosis of giant SK was made. The lesion was excised and the patient was kept under follow-up [Figure 1].

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Figure 1:

(a) Large verrucous well defined nodular growth present in the right medial inguinal region. (b) Lesion was excised completely. Pigmentation and scarring can be seen.

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Figure 2:

(a) Scanner view showing hyperkeratosis, follicular plugging, acanthosis and papillomatosis (H&E ×40) (b) High power photomicrograph of the same showing basal cell proliferation with increased melanin pigment. Dermis shows prominent pigment incontinence and melanophages (H&E ×200).

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SK are seldom more than 3 cm in size and when larger, they are referred to as giant SK.^[3] Our patient was a 60-year-old male who developed SK at an unusual photo-protected site. Giant SK in the genital area is a rare entity, with only a few reports in the literature.^[2-4] It should be differentiated from other conditions such as squamous cell carcinoma, Buschke– Löwenstein tumour or giant condyloma acuminata. A biopsy should be carried out to confirm the diagnosis.

The etiology of SK is unknown; however, few studies suggest an autosomal mode of inheritance with activation of the fibroblast growth factor receptor 3 signalling pathway.^[1] Tardío et al. suggested a strong association between genital SK and human papillomavirus (HPV)-6.^[5] In our case, no features suggestive of HPV infection were seen on histopathology.

SK has several morphological and histopathological variants. The morphological variants of SK include dermatosis papulosis nigra, stucco keratosis, inverted follicular keratosis, melanoacanthoma type and common flat SK.^[1] The histopathological variants include acanthotic type, adenoid or reticular variant, hyperkeratotic type, irritated SK, desmoplastic variant, clonal type, bowenoid type and adamantinoid type. Regardless of the histopathological variant, all types of SK are characterised by hyperkeratosis, papillomatosis and acanthosis.^[1] The present case showed adenoid/reticular variant of SK on histopathology, which is characterised by interdigitating basaloid cell proliferations with the absence of horn cysts.

The treatment options for SK include liquid nitrogen cryotherapy, curettage, laser therapy, shave excision or light electrodessication. The appropriate treatment modality should be decided based on the location and size. As appropriate, the larger lesions should be surgically excised with suturing or plastic reconstruction^.[1]