A lump in the middle of the groove between the two breasts may be related to sebaceous cysts, lipomas, breast hyperplasia and so on. 1. Sebaceous cysts: Sebaceous cysts are formed when the sebaceous ducts are blocked and the contents of the glands accumulate. Sebaceous cysts may grow between the two breasts and may appear as a hard ball-shaped lump, which may be accompanied by pain in some patients. 2. Lipoma: Lipoma is a common benign soft tissue tumor, fat parts of the body may grow lipoma, lipoma may grow in the middle of the ditch between the two breasts, and you can feel the obvious hard lumps when you touch it with your hands. 3. Breast hyperplasia: Breast hyperplasia is the most common benign breast disease, breast hyperplasia may occur in the middle of the groove between the two breasts, there may be a bulbous lump, and you may feel obvious pain. In addition, the symptoms may also be caused by local inflammatory lumps, trauma, etc. It is recommended that patients go to the hospital in time to do relevant examinations to clarify the specific causes of the disease, and then receive targeted treatment from doctors.