Girls chest especially small and hard lumps may be a normal phenomenon, may also be caused by breast hyperplasia, breast fibroids and other reasons. 1. Normal phenomenon: If it is an adolescent girl, breasts just started to develop, small breasts and hard lumps may be a symbol of breast development, usually a normal phenomenon, if there are no other uncomfortable symptoms, generally do not go to do special treatment. 2. Breast hyperplasia: Before menstruation, estrogen level may rise, so the breasts may be swollen, swelling and pain, usually after menstruation, swelling will gradually disappear, if the symptoms are not obvious, you can not do special treatment, if the situation is more serious, you should go to the hospital in time to intervene. 3. Breast fibroma: Breast fibroma is generally caused by excessive proliferation of breast mesenchymal stroma, which will form soft and smooth tumor tissues in the breast, so there may be the symptom of hard lumps in the breast. At the same time, hard lumps in the breast do not exclude the possibility of breast cancer, trauma and chronic inflammation, which need to be diagnosed for identification. It is recommended that those with hard lumps in the breast should go to the hospital for a comprehensive examination and relevant treatment according to the cause.