PECAM1 and vascular neoplasm: Considering the long-standing condition of Masson tumor, the relatively high recurrence rate, the appearance in preexisting vascular tumors, the Glut1 negativity and WT1 positivity and the accompanying pericytic layer and furthermore the constant positivity with different vascular markers (CD31, ERG), it seems that Masson tumor begins as a proliferative process but with time it transforms into a true benign neoplasm.