SLC2A1 and vascular neoplasm: We also concluded that Masson tumor begins as a proliferative process, but with time it transforms into a true benign neoplasm based on the following clinical and pathological findings: the long-standing condition of Masson tumor, the relatively high recurrence rate, the appearance in preexisting vascular tumors, the Glut1 negativity, WT1 positivity, the accompanying pericytic layer, and the constant positivity with different vascular markers (CD31, ERG).