A hard lump under the epidermis of the breast is possible due to breast hyperplasia, breast fibroma and breast cancer. 1. Breast hyperplasia: such a common benign breast disease, the patient will appear in the breast hard lumps, before and after menstruation will be obvious swelling and tingling, can be identified through the breast ultrasound symptoms. 2. Breast fibroma: it is due to the proliferation of fibrous tissue in the breast to form a mass, the patient can obviously feel the hardness, suffering from breast fibroma, usually do not have pain, there is no excessive adverse reaction. 3. Breast Cancer: Breast cancer is a serious malignant tumor, the clinical manifestation is the obvious lump in the breast, and the growth rate is fast, the activity is relatively poor. At the same time, hard lumps under the skin of the breast are also seen in breast inflammation, lipoma, skin disease, breast duct tumor, caused by breast trauma. When the patient has a hard lump under the epidermis of the breast, it is recommended to consult a regular hospital in time, and under the guidance and advice of the doctor after a clear diagnosis.