For years i've had a large lump on my forearm vein that balloons. if i raise my arm it goes down because the blood drains from it. when my arm hangs it fills with blood and gets really big if i'm exercising. it hurts if it's hit. is this an aneurysm?

No if it was an aneu: -rysm, it is a arterial condition, so if it was, U would feel it pulsate. This is most likely a connection 2 the deeper veins called a perforator, & at the connection 2 the superficial veins, there is usually a bulge, & is a normal physiological phenomenon.

Possible: Venous aneurysms do occur. If very large surgical ligation is possible. Since it empties with elevation,it is unlikely to be an arteriovenous malformation. May be unsightly but usually not dangerous.have your Pcp send you to a vascular surgeon to assess.

Vein: Possible trauma related weakness,somewhat more common with vigorous weight lifting Other possibilities include venous malformation Recommend evaluation and once completed treatment