Targetoid hemosiderotic hemangiomas (hobnail hemangiomas) are vascular lymphatic malformations: A study of 12 pediatric cases

Background Targetoid hemosiderotic hemangioma (THH), also called hobnail hemangioma, is a benign vascular lesion and thought to be of lymphatic origin. Objective We sought to perform a clinicopathologic analysis of cases diagnosed as THH in a tertiary care children's hospital. Methods Clinical and histopathologic data were obtained from a chart review of 12 confirmed pediatric cases of THH. To determine the presence or absence of lymphatic vessels in lesional biopsy specimens, we evaluated the expression of the lymphatic endothelial cell marker podoplanin using the D2-40 antibody. Wilms tumor-1 gene immunostaining and Ki-67 proliferation index were also performed to evaluate the proliferative nature of these lesions. Results Three children had a lesion since birth and 4 had a history of trauma before appearance of the THH. D2-40 immunostaining was positive in every case. Wilms tumor-1 gene immunostaining was negative in 9 cases, focally positive in two cases, and not performed in one case. The Ki-67 proliferation index was very low in all cases studied. Limitations The small number of cases and restriction to a pediatric population were limitations. Conclusion Our findings suggest that THH should be classified as a lymphatic vascular malformation.