What is a hematoma?

A hematoma is defined as a localized swelling that is filled with blood, typically resulting from an injury to a blood vessel. When a blood vessel is damaged, blood leaks into the surrounding tissues, creating a pool of blood that forms a noticeable swelling. This can occur in various locations in the body, such as under the skin or within muscles, and is often associated with bruising. Understanding the nature of hematomas is crucial in medical contexts, as they can vary in size and severity and may require treatment based on their location and the extent of bleeding.

The other options refer to different medical conditions; a mass of abnormal cells usually pertains to tumors, benign tumors relate specifically to non-cancerous growths, and a fluid-filled cyst describes a sac-like structure that contains liquid, which does not align with the definition of a hematoma.