There is an egg-sized swelling in the fossa of the heart, which is considered to be related to subcutaneous cyst, subcutaneous fibroma, subcutaneous lipoma and other factors. 1. Subcutaneous cysts: an egg-sized swelling in the fossa of the heart does not exclude the possibility of subcutaneous cysts, which are cystic structures formed by the dermis and the subcutis, and the cysts may contain fluids or other substances, and they belong to the more common skin damages, and they can occur in any part of the body. 2. Subcutaneous fibroma: this is a common benign tumor that occurs in the subcutaneous tissue area, its main symptom is a local lump, which may be accompanied by pain and discomfort, and with the development of the disease, the volume will further increase. 3. Subcutaneous lipoma: belongs to common soft tissue benign tumors, superficial lipoma can be seen as single or multiple subcutaneous confined lumps, which can occur in any fatty parts of the body, mainly composed of mature fat cells. An egg-sized lump at the opening of the heart fossa does not exclude the possibility of other causes, the patient should go to the hospital, cooperate with the doctor to improve the examination and determine the cause before handling and treatment.