Hobnail hemangioma was first reported by Santa Cruz and Aronberg in 19883
. A typical clinical appearance is a small solitary lesion consisting of a 2~3 mm-sized brown to violaceous papule surrounded by a thin, pale area and a peripheral ecchymotic ring. The characteristic targetoid appearance is due to peripheral hemorrhage and subsequent deposition of hemosiderin. However, these features are only present in a small percentage of cases and, most often, the clinical appearance is that of a red-blue or brown papule.
The etiology of hobnail haemangioma is unknown, but traumas to a pre-existing hemangioma and the influences of sex steroid hormones have been proposed4-6
. Interestingly, some lesions in females change during the menstrual cyce or pregnancy.
Published reports of hobnail hemangioma reveal an equal gender incidence, lwith an age range of presentation of 5~67 years. It is identified more frequently in younger persons3
. There are 10 case reports in the Korean literature7-16
(). In those cases, skin lesions developed at 3~32-years-of-age. Nine patients had a solitary lesion, but one patient had two papules on the upper back and arm8
. Five lesions arose in the lower extremities, four on the trunk and two on the upper extremities. Our 'case 1' is the youngest patient reported in Korea so far and is the first patient that has had the skin lesion since birth. 'Case 2' is the second case with two lesions after the first one reported in the Korean literature8
Reported cases of hobnail hemangioma in the Korean literature
Histologically, characteristic features are irregularly dilated vesHsels lined by hobnail endothelial cells in the superficial dermis and collagen-dissecting, rather narrow vessels in deeper dermis. The hobnail endothelial cell has scanty cytoplasm and rounded nuclei that protrude into theumina. Focally, intraluminal papillary projections can be seen in the superficial blood vessels. The vascular channels in the deeper dermis become much less conspicuous and eventually disappear completely. The whole architecture is wedge l-shaped, with a prominent superficial component. In the later stages, extensive stromal hemosiderin deposits are commonly seen.
The clinical differential diagnoses include melanocytic nevus, dermatofibroma, hemangioma and insect bite reaction. The microscopic differential diagnoses are the patch stage of Kaposi's sarcoma, retiform hemangioendothelioma, solitary angiokeratoma, progressive lymphangioma and eosinophilic hemangioma. It is especially important to distinguish hobnail hemangioma from the patch stage of Kaposi's sarcoma. Factors favoring Kaposi's sarcoma are the presence of plasma cells, spindle-shaped cells and apoptotic endothelial cells17
The tumor origin is controversial. Santonja and Torrelo18
suggested a vascular origin for hobnail hemangioma since it had positive reaction with Factor VIII-related antigen, CD31 and CD34. However, Franke et al.19
proposed that this tumor has a lymphatic origin because it revealed positive reaction with D2-40 and CD31, and a negative reaction with CD34. In our first case, immunohistochemistry revealed a mild focal positive reaction with CD34 and D2-40 and strong positive reaction with CD31. These results imply that the origin is vascular endothelial cells, not lymphatic endothelial cells.
To our knowledge, all reported cases are acquired type. Here, we report two cases of hobnail hemangioma that are peculiar in that one is congenital and the other is multiple.