What is the significance of vortex vein invasion in uveal melanoma?

Intravascular Presence of Tumor Cells as Prognostic Parameter in Uveal Melanoma: A 35-Year Survey

“…Figure 1 demonstrates this situation: it can be observed that ingrowth of tumor cells into the vorticose vein occurred, which may then allow tumor cells to migrate outside the eye. 28 This can then be observed macroscopically as an extra large and dark vorticose vein on the sclera after enucleation.…”