Atypical clinical and dermoscopic features of hobnail hemangioma

Sir,

A 36-year-old woman (Patient 1) with skin phototype-V, presented with a 10-month history of an asymptomatic pigmented lesion on the abdomen. Cutaneous examination revealed a solitary 1.5 cm × 1 cm, firm, non-tender, pigmented plaque on the abdomen [Figure 1a]. Differential diagnosis of dermatofibroma, dermatomyofibroma and melanocytic nevus was considered. Dermoscopic examination under nonpolarized contact mode (HEINE DELTA20® Dermatoscope, Germany, 10 × magnification) showed a cerebriform pattern. The dermoscopic features observed were a gray background, comedo-like openings, linear irregular crypts and keratotic plugs [Figure 1b]. The excisional biopsy of the lesion showed multiple lymphangioma-like dilated spaces with intraluminal projections lined by hobnail endothelial cells in the upper dermis, and slit-like vascular spaces dissecting the collagen bundles along with perivascular lymphocytic infiltration in the lower dermis. Perl’s Prussian blue stain demonstrated dermal hemosiderin [Figure 2].

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Figure 1a:

Solitary firm pigmented plaque on the abdomen

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Figure 1b:

Dermoscopic examination (under nonpolarized contact mode, HEINE DELTA20^® Dermatoscope, Germany, ×10) demonstrating a cerebriform pattern, a gray background, comedo-like openings, linear irregular crypts and keratotic plugs

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Figure 2a:

Multiple lymphangioma-like dilated spaces in the upper dermis lined by hobnail endothelial cells with an overlying hypertrophic and hyperpigmented epidermis (H and E, ×100)

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Figure 2b:

Slit-like vascular spaces dissecting the collagen bundles in the lower dermis (H and E, ×100)

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Figure 2c:

Perivascular lymphocytic infiltration (H and E, ×400)

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Figure 2d:

Special stain highlighting hemosiderin (Perl’s Prussian blue stain, ×100)

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A 44-year-old man (Patient 2) with skin phototype-V had a slow-growing lesion on the abdomen for the last 6 months. Cutaneous examination revealed a solitary 5 mm × 5 mm firm non-tender shiny dome-shaped skin-colored nodule on the abdomen [Figure 3a]. Differential diagnosis of solitary neurofibroma, solitary circumscribed neuroma and fibroepithelial polyp was considered. Dermoscopy of the nodule demonstrated a gray homogenous area, along with brown peppering [Figure 3b]. Shave biopsy of the lesion showed, proliferating endothelial cells admixed with multiple dilated vascular spaces lined by hobnail endothelial cells. Perl’s Prussian blue showed occasional hemosiderin deposition [Figure 4].

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Figure 3a:

Solitary firm non-tender dome-shaped nodule on the abdomen

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Figure 3b:

Dermoscopic examination (under nonpolarized contact mode, HEINE DELTA20^® Dermatoscope, Germany, ×10x) demonstrating a gray homogenous area and brown peppering

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Figure 4a:

Proliferating endothelial cells admixed with multiple dilated vascular spaces in the dermis (H and E, ×50)

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Figure 4b:

Dilated vascular spaces lined by hobnail endothelial cells (H and E, ×100)

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Figure 4c:

Hobnail endothelial cells (H and E, ×400)

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In both cases, a final diagnosis of hobnail hemangioma was made based upon the histopathological findings.

Hobnail hemangioma, also known as targetoid hemosiderotic hemangioma is a benign cutaneous vascular lesion. It commonly occurs in young to middle-aged persons and has a slight female preponderance. A solitary asymptomatic papule on the extremities and trunk, in a young to middle-aged adult, is the most common presentation of hobnail hemangioma. The size ranges from 0.6 cm to 2 cm. As the name suggests, a targetoid appearance with a central violaceous to red macule or papule surrounded by a pale rim, and an outermost ecchymotic ring, usually provides a clue to the diagnosis. The targetoid appearance is not universal; cases with nontargetoid appearance have been described.^1,2 In the case of a nontargetoid or atypical presentation, it can be mistaken for other cutaneous vascular (hemangioma, angiokeratoma, Kaposi’s sarcoma), melanocytic (melanocytic nevus, dysplastic nevus, melanoma) and fibrohistiocytic (dermatofibroma, fibroma) tumors. Both of the described cases neither had a targetoid pattern nor any clinical clue like reddish-violaceous color, to suggest the vascular nature of the lesions. In the first case, a pigmented firm plaque, we considered differentials of dermatofibroma, dermatomyofibroma and melanocytic nevus. In the second case, a firm skin-colored dome-shaped nodule, we considered differentials of solitary neurofibroma, solitary circumscribed neuroma and fibroepithelial polyp.

The dermoscopic examination is a rapid, noninvasive procedure that provides subtle clues to the diagnosis of a cutaneous lesion. For a vascular malformation/ tumor, the presence of lagoons/clods of varying colors during dermoscopic examination is a constant feature. Although not specific to any particular vascular tumor/ malformation, their presence guides the clinicians to rule out nonvascular etiology. A recent review of dermoscopic features of hobnail hemangioma described red lacunae, dark lacunae, whitish structures, a central homogeneous area, intermediate yellowish areas, peripheral red-violaceous ring, vascular structures and pigment network.² Zaballos et al. analyzed 35 cases of hobnail hemangioma and reported dermoscopic features such as reddish-violaceous, and brown homogenous areas (85.7%), red and dark lacunae (74.3%), chrysalis (42.8%), vascular structure (40%) and delicate pigment network (14.3%).³ The various patterns observed by them were; a central lacuna and peripheral homogenous area with or without intermediate skin-colored, yellow or white circular homogeneous area (71.4%), diffuse reddish-violaceous homogenous area and delicate pigment network and red lacuna alone (single report). The other dermoscopic features reported for hobnail hemangioma are enlisted in Table 1.^4-10 From the various reports, it is evident that a lagoon of variable color, with or without a targetoid pattern, is a consistent feature of hobnail hemangioma. In the two of our described cases, dermoscopy neither demonstrated a targetoid pattern nor had any dermoscopic clue to the diagnosis of a vascular lesion, thus mislead the diagnosis. The first case dermoscopically mimicked a dermatofibroma or seborrheic keratosis due to the presence of cerebriform pattern, and gray background. Another rare clinical mimic, aneurysmal fibrous histiocytoma, commonly demonstrates a blue homogenous area that may accompany other shades of color like pink, reddish-brown or white. The blue homogenous area corresponds to the dermal hemosiderin deposition. Other features described are pigment network, branched streaks, white crystalline structure, a rainbow pattern and vessels ranging from dotted, polymorphous and linear irregular vessels. The second case dermoscopically mimicked a neurofibroma due to a featureless pattern. The dermoscopic difference between hobnail hemangioma, neurofibroma and dermatofibroma is mentioned in Table 2.^2,3,11-14 In case-1, the hyperplastic and hyperpigmented epidermis masked the dermoscopic vascular structures. In case-2, along with mild hyperplastic and hyperpigmented epidermis, the relatively lower dermal location of the vascular lesion may be responsible for the absence of the dermoscopic vascular feature. The final diagnosis of both cases was revealed by histopathological examination.

In conclusion, we describe two cases of hobnail hemangioma with atypical clinical and dermoscopic features. The vascular nature of the hobnail hemangioma was concealed due to the absence of clinical and dermoscopic vascular features like reddish-violaceous color and vascular lagoons, respectively. At times, the dermoscopic examination can be misleading, especially in cases of atypical clinical presentation, in which case a histopathological examination is essential for the diagnosis.