Superficial vein thrombosis
Superficial vein thrombosis (SVT) is a blood clot formed in a superficial vein; a vein near the surface of the body. Usually there is thrombophlebitis, which is an inflammatory reaction around a thrombosed vein, presenting as a painful induration (thickening of the skin) with redness.
Source: Wikipedia — Superficial vein thrombosis (CC BY-SA 4.0)