A solitary angiokeratoma on the toe of a teenaged girl

Abstract

An angiokeratoma is a benign vascular lesion that appears as one or more red to black papules with a verrucous surface. Histologically, it is defined by ectatic, thin-walled vessels in the papillary dermis, acanthosis with elongated rete ridges, and compact hyperkeratosis. Solitary angiokeratoma is one of five defined subtypes of angiokeratoma. We report the case of an 18-year-old woman with a “wart” that had been present for many years. After treatment with several over-the-counter wart therapies, several rounds of paring plus cryotherapy, and Candida antigen injections failed, a shave biopsy was taken to remove the lesion, and histopathologic examination was consistent with an angiokeratoma. This case demonstrates the importance of considering angiokeratoma in the differential diagnosis of a wart, particularly one recalcitrant to treatment.

The most common diagnosis for a verrucous papule in the plantar aspect of the foot is a plantar wart; however, other diagnoses must be considered in cases that are recalcitrant to treatment. Here, we present a case of a solitary angiokeratoma (SA) and discuss differential diagnoses for a verrucous papule on the plantar aspect of the foot and how they are distinguished clinically, histologically, and immunohistochemically.

CASE DESCRIPTION

An 18-year-old woman presented to our clinic for treatment of a “wart” that had been present for several years. The lesion was occasionally painful but otherwise she denied any symptoms other than undesirable cosmetic appearance. Prior to presentation, she had tried many over-the-counter wart treatments without success. Physical exam revealed a 4 mm verrucous papule with areas of visible hemecrust on her right plantar second toe (Figure 1). Over the course of several months, we proceeded with multiple in-office treatments for her wart, including paring with cryotherapy as well as three rounds of Candida antigen injections into the base of the lesion. After none of these treatments was successful, a shave biopsy was taken for analysis (Figure 2). Histological analysis revealed ectatic, thin-walled vessels in the papillary dermis, elongated rete ridges, and compact hyperkeratosis. Immunohistochemically, the tissue was WT-1 and GLUT-1 negative in endothelial cells (Figure 2c, 2d). D2-40 was partially positive within the endothelial lining (Figure 2b).

Figure 1.

Solitary angiokeratoma on the plantar aspect of the second toe.

Figure 2.

Solitary angiokeratoma on the plantar aspect of the second toe, shave biopsy. (a) Hematoxylin and eosin staining, 2×. (b–d) Immunohistochemical stains, 5×: (b) D2-40 is partially positive within the endothelial lining. (c) GLUT-1 and (d) WT-1 are negative.

DISCUSSION

Histopathological and immunohistochemical findings were consistent with SA. Histologically, angiokeratomas show ectatic, thin-walled vessels in the papillary dermis that are often near or in contact with the epidermis, acanthosis with elongated rete ridges, and compact hyperkeratosis.^1,2 Immunohistochemically, angiokeratomas are WT-1 and GLUT-1 negative,³ and SAs are usually focally positive for D2-40.^4,5 Thus, our histological and immunohistochemical findings, as well as the clinical appearance of a singular lesion, support the diagnosis of SA.

The term angiokeratoma was introduced by Vittorio Mibelli in 1889, describing vascular lesions on the hands and feet of a young girl.⁶ Since then, five types of angiokeratoma have been defined: angiokeratoma corporis diffusum, angiokeratoma circumscriptum, Fordyce’s angiokeratoma, angiokeratoma of Mibelli, and SA.^1,2 SA comprises around 70% to 83% of all angiokeratomas.¹ Clinically, a SA presents as a dark keratotic papule, measuring 2 to 10 mm in diameter, usually on the lower extremitity.¹

Clinical appearance and immunohistochemical staining distinguish SA from other defined angiokeratoma types. Angiokeratoma circumscription lesions are much larger, angiokeratoma of Fordyce occurs on the genitalia, and angiokeratoma diffusum presents with many small papules, often as a symptom of Fabry disease.¹ Clinically, angiokeratoma of Mibelli often presents on the hands and feet of girls and young women, so this diagnosis was considered.¹ However, angiokeratoma of Mibelli stains D2-40 negative, while SA often stains D2-40 positive. Thus, the focally positive D2-40 staining seen in our patient’s angiokeratoma was more consistent with a SA.^1,4,5

Other differential diagnoses include microcystic cutaneous lymphatic malformation (MCLM), verrucous hemangioma, and plantar wart. MCLM is a histologic and immunohistochemical mimic of SA.^7,8 Clinically, MCLM typically presents as a congenital malformation at or soon after birth as 2 to 4 mm clear vesicles typically in the neck and head region, so we favored the diagnosis of SA.⁹ Verrucous hemangioma appears similar to SA histologically, but is typically D2-40 negative and GLUT-1 positive immunohistochemically.¹⁰ A plantar wart can be distinguished from SA histologically; plantar warts appear papillomatous with a compact stratum corneum, coarse hypergranulosis, and characteristic koilocytic change.¹¹

SA is benign and typically asymptomatic, so treatment is not necessary. However, patients may elect treatment due to disfiguration, bleeding, or pain caused by the lesion. Traditionally, SA treatment has consisted of cryotherapy, cautery, excision, electrosurgery, and laser treatments.¹²