Breast hematoma is a collection of blood within the breast. It arises from internal bleeding (hemorrhage) and may arise due to trauma (breast injury or surgery) or due to a non-traumatic cause. Breast hematoma is a collection of blood within the breast. It arises from internal bleeding (hemorrhage) and may arise due to trauma (breast injury or surgery) or due to a non-traumatic cause. Symptoms may include visible discoloring (ecchymosis), breast pain, and swelling. The symptoms may be similar to those of fibrocystic breast changes.