Superficial vein thrombosis is not dangerous in most cases, but sometimes it depends on the specific circumstances of the vein thrombosis. Superficial vein thrombosis can occur everywhere in the body, including the upper and lower extremities and the middle part of the torso. In general, there are two trends in thrombosis: 1. This superficial vein thrombosis becomes confined and no longer extends upward or downward, and after 2-3 weeks it begins to show gradual resorption and mechanization, with light brown pigmentation of the skin, which is not dangerous. 2. Less frequently, it regresses. The thrombus will continue to progress up or down the superficial veins, sometimes through the valves into the deep veins, and sometimes through the penetrating branches into the deep veins. In this case the thrombus will dislodge within the deep vein, enter the heart along the vein, and then enter the pulmonary artery through the pumping of the heart, while leading to pulmonary embolism, which may be directly life-threatening, so it is only in this very rare case that it is dangerous.