Penile Porokeratoma: A Case Report

Dear Editor,

Porokeratoma is a rare dermatological condition characterized by acanthotic lesions with verrucous or scaly surfaces. This condition is relatively rare, with only a limited number of cases documented in the literature. Unlike typical porokeratosis, which features a single cornoid lamella, porokeratoma presents with multiple cornoid lamellae throughout the biopsy specimen. While usually found on the limbs, this condition can occasionally involve unusual sites, including the genital area. The rarity of genital involvement and its potential to be confused with other conditions, such as viral warts, highlights the importance of accurate diagnosis and appropriate management to prevent potential malignant transformation.[1,2]

A 30-year-old man presented with a single, elevated lesion on the penile shaft for six months, which was asymptomatic and gradually enlarging. He had no history of high-risk sexual behavior, immunosuppression, or other comorbidities. On physical examination, a solitary, round-to-oval, pinkish-erythematous verrucous plaque was observed on the distal penile shaft [Figure 1], while the rest of the genital and mucocutaneous examination was normal. Histopathological examination showed marked hyperkeratosis and papillomatosis along with alternating thick and broad cup-shaped invaginations composed of columns of hypereosinophilic parakeratotic keratinocytes [Figure 2a]. These columns had a noticeable absence of granular layers with larger and paler keratinocytes underneath and a few dyskeratotic cells [Figure 2b]. However, immunohistochemistry for human papillomavirus could not be done due to resource constraints. Based on clinical and histopathological features, the patient was diagnosed as a case of penile porokeratoma and was prescribed 5% 5-fluorouracil cream for alternate day application, resulting in resolution within six weeks [Figure 3].

Figure 1.

Erythematous verrucous scaly plaque on distal penile shaft

Figure 2.

Histological section showing (a) epidermal hyperkeratosis, papillomatosis, and acanthosis in the center with dilated blood vessels, surrounded on either side by broad and thick column (black line) of hypereosinophilic parakeratotic keratinocytes (H and E; 100×); (b) Higher magnification showing broad column of parakeratosis (black line) with absent granular layer underneath and adjoining pale (black arrows) keratinocytes along with dyskeratotic (red arrow) cells (H and E; 400×)

Figure 3.

Resolution following treatment

Porokeratoma, also known as porokeratotic acanthoma, is a dermatological condition resembling porokeratosis. It commonly presents as scaly papules, plaques, or nodules, although verrucous lesions, as seen in our case, are relatively rare. In the initial description by Walsh et al., all 11 reported cases exhibited a solitary lesion, predominantly located on the limbs, and were more frequent in males.[1] Histological examination revealed multiple cornoid lamellae throughout the biopsy specimen, alongside acanthosis and hyperplasia. This differs from typical porokeratosis, which usually presents with a single cornoid lamella located at the lesion’s periphery, corresponding to the clinically observed elevated margin. Additionally, porokeratoma does not exhibit the central epidermal atrophy commonly associated with porokeratosis. The cornoid lamella, a distinct epidermal reaction pattern, is characterized by focal parakeratosis with an absent granular layer underneath, sometimes accompanied by dyskeratotic keratinocytes and basal cell vacuolization. Although this feature is typical of porokeratosis, it may also occur in other conditions, such as viral warts and actinic keratosis.[1,2]

The cases reported by Walsh et al.[1] did not present with concurrent skin lesions typical of porokeratosis or any associated comorbidities. However, subsequent reports have identified cases with multiple lesions and associated comorbidities, such as ankylosing spondylitis, leukemia, and coexistent lesions of disseminated superficial porokeratosis.[3] Additionally, human papillomavirus has been detected in some cases of porokeratoma.[4] Porokeratoma can present in unusual locations, including the nipple, trunk, and buttocks, with involvement of the penile shaft and other genital skin being rare. Joshi et al.[5] described 10 cases with similar clinical presentations and reaction patterns involving the genital area, which they termed “pruritic porokeratotic peno-scrotal plaques” rather than “porokeratoma.” In their retrospective study, the clinical differentials included viral warts and lichen simplex chronicus. They observed well-defined lesions with a rough or granular surface over the penile region, giving the impression of condyloma acuminata but lacking a thready margin. Notably, the base of each cornoid lamella displayed slight vacuolization of cuticular cells, as also noted in our case in the form of larger and paler keratinocytes. Additionally, in one-third of the cases, the cornoid lamellae originated from eccrine and follicular structures.[5]

Differential diagnoses of penile porokeratoma include viral warts or condyloma acuminata, distinguishable histopathologically by the presence of hypergranulosis and koilocytic changes. Verruciform xanthoma may clinically resemble porokeratoma; however, the presence of foamy or vacuolated cells in the papillary dermis differentiates it. Another differential diagnosis is hypertrophic lichen planus, characterized by focal lichenoid or interface dermatitis changes at the dermoepidermal junction.

Porokeratoma is generally a benign condition, with treatment primarily focused on symptom relief. Effective local treatments include 5-fluorouracil, cryotherapy, and ablative lasers. Some authors recommend excision of the lesion, particularly in cases of solitary lesions, due to the potential risk of malignant transformation. For multiple disseminated lesions, systemic agents, such as acitretin, may be considered.[5]

In summary, porokeratoma is a distinct condition from porokeratosis, with a possibility of malignant transformation necessitating close follow-up.

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The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)

We have not used artificial intelligence in the preparation of this manuscript. We have referred to the publisher’s policy on the use of AI as outlined in the Information for Authors and assume full responsibility for the content of our manuscript.

Funding Statement

Nil.