Nipple inversion without lump is not necessarily breast cancer, congenital nipple inversion or acquired mastitis, blocked milk ducts can also cause nipple inversion. 1. Congenital nipple inversion: Congenital nipple inversion is a normal physiological phenomenon, which refers to the congenital nipple lower than the breast plane in the process of growth and development of women, and it is not a pathological phenomenon, so there is no need to carry out special treatment. 2. Mastitis: Mastitis or blockage of breast ducts may cause localized swelling of the breast and lead to nipple inversion in the breast, usually occurring in breastfeeding women or pregnant women. 3. Breast cancer: If there is obvious skin ulceration, bleeding and abscess on the surface of the nipple, you need to be alert to the possibility of breast cancer, and you can go to the hospital for imaging examination or pathological sampling, which can directly determine whether there is a malignant tumor. After the symptoms of inverted nipple appear, it is recommended to go to the hospital for breast examination regularly. People with a family history of breast cancer need to be screened as early as possible.