Hobnail hemangioma (HH) is currently classified as a benign vascular tumor, although it is not well understood whether this lesion differentiates toward blood or lymphatic endothelial cells. Immunostaining with the endothelial marker Wilms tumor 1 (WT1) helps distinguish between vascular neoplasms and malformations, being positive in the former and negative in the latter.

We sought to investigate WT1, human herpesvirus 8 latent nuclear antigen, D2-40, and Ki-67 immunoprofile in HH, to gain further insight into its histogenesis.

We evaluated 52 HHs collected in Dermatohistopathologische Gemeinschaftslabor, Friedrichshafen, Germany. Immunohistochemical expression of WT1 was performed in all cases. Ten of 52 lesions were also studied for D2-40 and Ki-67 staining and 12 lesions were stained for human herpesvirus 8 latent nuclear antigen.

All 52 HHs were completely negative for WT1 immunostaining. Immunohistochemistry performed in 10 HHs showed diffuse and strong positive staining for D2-40 in 8 lesions and focal positivity in two. All cases tested showed negative staining for Ki-67 and human herpesvirus 8 latent nuclear antigen.

There are no limitations.

Although the exact histogenesis of HH is unknown, most of the performed immunohistochemical studies support a lymphatic line of differentiation. However, on the basis of the WT1 negativity, we believe that HH is better considered as a lymphatic malformation rather than a lymphatic neoplasm.