The reason for the bulge in the armpit: 1, the formation of parametrium, which is common in pregnant women and maternity, is caused by excessive secretion of hormones in the body, do not worry too much, with the end of breastfeeding, or after childbirth, the lumps can gradually subside, but if there is no obvious subside, you need to go to the hospital to improve the relevant examination to perform surgery. 2, fat accumulation caused by, this is often due to excessive obesity caused by, generally do not worry too much, can The majority of the disease is not treated by surgery, but if it is rapidly increasing or painful, it is necessary to perform surgery and pathological examination. 4.Lymph node enlargement is the cause.