A hematoma, or haematoma, is a collection of bloo, generally the result of hemorrhage, or, more specifically, internal bleeding. Hematomas exist as bruises (ecchymoses), but can also develop in organs. Some hematomas form into a welt-like formation that is hard to the touch, which is a sac of blood that the body creates to keep internal bleeding to a minimum. In most cases the sac of blood eventually dissolves; however, in some cases they may continue to grow or show no change. If the sac of blood does not disappear it may need to be surgically removed.