A hard lump is not always found inside the breast, but if a hard lump is found inside the breast, it often indicates that the breast is suffering from some disease. In the case of postpartum women, it may be caused by a build-up of breast milk. In general, it may be a serious breast enlargement, breast fibroid, or even breast cancer. Therefore, further examinations such as breast ultrasound, mammography, breast MRI, etc. are needed, and in some cases, puncture biopsy or excisional biopsy of the lump is required to clarify the nature. If the lump is considered to be caused by breast accumulation, active lactation treatment is needed, as well as dietary adjustments, such as drinking more water and consuming fresh fruits and green vegetables. If it is a benign hyperplasia of the breast, the mass can be removed. If the tumor is considered malignant, radical excision of the tumor with lymph node dissection and later chemotherapy and targeted therapy may be required.