What is a hematoma?

A hematoma is defined as a localized swelling that occurs when blood collects outside of blood vessels, typically due to a break in the wall of a blood vessel. When blood leaks into the surrounding tissues, it creates a mass that is often visible as swelling and can feel firm or tender to the touch. This condition can arise from trauma, surgical procedures, or certain medical conditions that affect blood clotting.

In contrast, other options describe different medical conditions that are not related to the definition of a hematoma. For instance, a heart condition would pertain to disorders that affect the function or structure of the heart itself, rather than blood collection in tissues. A benign tumor of the liver involves a growth of liver cells that does not invade neighboring tissues or spread throughout the body. An acute infection signifies the body's response to a pathogen such as bacteria or viruses, resulting in symptoms like fever and inflammation, which differs from the mechanical phenomenon of blood accumulation that characterizes a hematoma.