a hematoma (us spelling) or haematoma (uk spelling) is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. a hematoma is benign and is initially in liquid form spread among the tissues including in sacs between tissues where it may coagulate and solidify before blood is reabsorbed into blood vessels. an ecchymosis is a hematoma of the skin larger than 10mm.