An ecchymosis is a bruise. A hematoma is a blood clot. A Hematoma is a collection of clotted blood outside a blood vessel. A Ecchymosis(commonly called a bruise) is blood leaked out from a blood vessel under the skin. Hematomas are swellings and has more of a three dimensional character to it, while ecchymoses are flat. As well, hematomas may occur in any organ and not just under the skin like ecchymoses.