Final answer:
A mass of blood in the tissues caused by a break in a blood vessel is called a hematoma.
Step-by-step explanation:
The mass of blood that has pooled in the tissues due to a break in the wall of a blood vessel is called a hematoma.
Blood, being a fluid connective tissue, contains various components such as red blood cells, white blood cells, and platelets, which circulate in a liquid extracellular matrix called plasma. When injury occurs, and a blood vessel is severed, these components can leak out and collect in the tissue, forming a hematoma. This is different from a hemorrhage, which is the actual process of bleeding or the flow of blood. It is also unrelated to a soft callus, which refers to a stage in bone healing, or an angioma, which describes a benign tumor derived from blood vessel walls.