Hobnail hemangioma reclassified as superficial lymphatic malformation: a study of 52 cases.

BACKGROUND: 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.

OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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.

LIMITATIONS: There are no limitations.

CONCLUSIONS: 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.