A haematoma, or hematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise. Internal bleeding is generally considered to be a spreading of blood within the abdomen or skull, not within muscle.
It is not to be confused with hemangioma which is an abnormal build up of blood vessels in the skin or internal organs.
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