Girls with hard nodes in their breasts usually menstruate in about 1 to 2 years, but it is also possible for breast disease to cause the nodes, and the timing of menstruation is not easy to determine. The appearance of hard lumps in girls’ breasts suggests that the breasts are beginning to develop and the mammary glands are beginning to enlarge, suggesting the development of secondary sexual characteristics, usually after the age of eight. After breast development, pubic hair grows on the perineum and menstruation usually occurs in 1 to 2 years. The presence of breast nodules before the age of 8 is often indicative of precocious puberty, and medical attention should be sought as soon as possible to determine the cause of the condition. Hard lumps in girls’ breasts may also be caused by breast hyperplasia, which may be associated with an abnormal increase in estrogen and the formation of hard lumps, or hard lumps caused by breast tumors, and it is not easy to determine whether or not it is time to have a menstrual period. Girls with hard lumps in their breasts should seek medical attention to determine the cause of the lumps so as not to delay their condition.