7-year-old baby girl chest has a hard lump may be pubertal breast development or local soft tissue infection, etc., specific to combine the child’s body in all aspects of the situation and other comprehensive judgment. 8~15 years old is the time of breast development, there is also a part of the little girl is 8 years old before the development of the breast may feel the lump, this time need to be alert to the problem of precocious puberty, precocious puberty, hormone secretion is too much, may cause the development of the baby’s chest. If the hard lump in the baby’s chest is caused by a local soft tissue infection, the local inflammatory response leads to the production of hard lumps, often manifested as local redness, swelling, pain, fever, etc. in the chest, and if there is abscess formation, the local area may have fluctuating sensations. 7-year-old baby chest has a hard lump in addition to the above reasons, but also other reasons, if the hard lump has not been eliminated, or accompanied by other uncomfortable symptoms, it is recommended that parents take their children to the hospital as soon as possible to identify the cause, and targeted treatment.