Vascular tumors and malformations can be challenging to diagnose. Although they may initially appear very similar, they have distinct clinical courses and management. Wilms tumor 1 (WT1) gene expression has been reported in many different tumors including hematologic malignancies and some solid tumors.

We sought to evaluate the expression of WT1 in 126 vascular lesions (64 vascular tumors, one Masson tumor, and 61 vascular malformations).

Based on the International Society for the Study of Vascular Anomalies classification of vascular anomalies, we studied the expression of WT1 in vascular tumors composed of infantile hemangioma, congenital hemangiomas (non-involuting, rapidly involuting, and not otherwise specified), pyogenic granuloma, tufted angioma, cherry angioma, Kaposi sarcoma, and angiosarcoma. We also studied WT1 expression in vascular malformations composed of angiokeratoma/verrucous hemangioma, combined vascular malformations, venous malformations, glomuvenous malformations, lymphatic malformations/lymphangioma, telangiectasia, and targetoid hemosiderotic hemangioma.

All vascular tumors and proliferations had positive WT1 cytoplasmic endothelial immunostaining whereas only 3 vascular malformations were WT1 positive. Moreover the positivity of WT1 in these vascular malformations was focal and involved only re-endothelialized neovessels within thrombi.

The low number of malignant vascular tumors is a limitation.

Immunohistochemical detection of WT1 could be a useful tool to routine evaluation of vascular anomalies allowing the distinction of vascular tumors and proliferations from vascular malformations. Staining for WT1 may guide the clinician in difficult cases, as positive results would suggest a proliferative vascular lesion whereas negative results might point to a vascular malformation.