Subcutaneous lipoma and sebaceous cysts may be the cause of the mass of flesh under the skin in the upper fossa of the sternum. 1. Subcutaneous lipoma: subcutaneous lumps of flesh in the upper fossa of the sternum may be caused by subcutaneous lipoma, subcutaneous lipoma is a common benign tumor on the body surface, it is a kind of painless lump in the subcutaneous fat layer, with clear boundaries and good mobility, usually without obvious pain, and it can be completely removed through local anesthesia. 2. Sebaceous cysts: a mass of flesh under the skin in the upper fossa of the sternum may also be caused by sebaceous cysts, which need to be diagnosed by ultrasound, and if it is a sebaceous cyst, it can be completely excised under local anesthesia. Patients with subcutaneous lumps in the upper fossa of the sternum are advised to go to the hospital in time, clarify the cause of the disease and then carry out standardized treatment according to the doctor’s guidance.