During non-pregnancy and non-lactation periods, fluid flowing out of the nipple when squeezed is called nipple discharge. Nipple overflow is one of the common symptoms of breast diseases. According to statistics, those who visit the doctor with nipple overflow as the first symptom account for 3 – 14% of breast diseases, and the incidence is second only to breast lumps and breast pain. 1, if the nipple overflow is a single nipple overflow, most of them are related to the following breast diseases: (1) Ductal dilatation of the breast: some patients suffering from this disease, the first symptom of early nipple overflow. The color of the overflow is mostly brown, with a few being bloody; laboratory tests show a large number of plasma cells and lymphocytes without tumor cells. The disease is more common in non-lactating or menopausal women over 40 years of age. The lump is often less than 3 cm in diameter and the ipsilateral axillary lymph nodes may be enlarged, soft and painful to the touch. The lymph nodes of the same side of the axilla may be enlarged, soft, and painful to the touch. If the lump is complicated by infection, the inflammatory manifestation of the lump is red, swollen, hot and painful. (2) Intraductal papilloma: This disease is common in people aged 40 – 50 years old, 75% of the tumors occur in the area adjacent to the nipple, the tumor is small, with a tip and villi, and there are many thin-walled blood vessels, so it is easy to bleed. The tumor cells can be found in the overflow of laboratory test. Sometimes when the patient palpates the breast carefully, a cherry-sized mass under the areola can be found, which is soft, smooth and mobile. (3) Cystic hyperplasia of the breast: it is more common in women of childbearing age. Some patients have yellow-green, brown, bloody or colorless plasma-like nipple discharge, and no tumor cells are present in the discharge on laboratory examination. This disease has two characteristics: First, it is characterized by periodic swelling and pain in the breast, which often occurs or is aggravated during the premenstrual period, and is not minded by the patient in mild cases, but can affect work and life in severe cases. The second is that breast lumps are often multiple and can be seen on one or both sides, or can be confined to a part of the breast or scattered throughout the breast. The lumps are nodular in shape and vary in size, tough but not hard, not adherent to the skin, and poorly defined from the surrounding tissues. (4) Breast cancer: Some patients with breast cancer have bright red or dark red nipple overflow, sometimes clear water overflow, colorless and transparent, occasionally sticky, leaving no trace after overflow, and cancer cells can be found in the overflow. The onset of the disease is slow. Patients may unintentionally find breast lumps, mostly located in the upper inner or upper outer limit, painless and gradually larger. In advanced stages, orange peel-like skin changes and satellite nodules appear at the lesion site. The axillary lymph nodes are enlarged, hard, and fuse with each other to form a mass as the disease progresses. 2, there are also, need to pay attention to: (1) overflow is true or false. True overflow refers to the flow of fluid from the ducts of the breast. Pseudofluid is common in those with sunken nipples, due to the accumulation of epidermal cells in the sunken area of the nipple, causing a small amount of liquid-like bean curd-like exudate, often with a foul odor. Once the sunken nipple is pulled out and local cleanliness is maintained, the “overflow” will disappear. (2) Whether the overflow is bilateral or unilateral. Bilateral overflow is physiological, and most women will still have a small amount of milk secretion if they stop breastfeeding for a year. In mid to late pregnancy, some pregnant women may express a little light-colored colostrum from both breasts. A few women may also experience a short period of milk overflow after a strong orgasm due to high blood vessel congestion in the breasts, breast distention, and erect nipples. When women go through menopause, some of them produce small amounts of milk due to endocrine disorders. All of the above are physiological conditions and are not pathological. However, bilateral nipple overflow can also be pathological, such as a condition called amenorrhea-overflow syndrome, which is caused by pituitary microadenoma and is associated with amenorrhea, headache, narrowing of the visual field, and elevated prolactin in the blood, in addition to overflow. CT brain examination can confirm the diagnosis. Another type of double nipple overflow is seen in patients with few mastopexy. (3) Whether the overflow is uniportal or multi-portal. The nipple has 15 – 20 openings for the milk ducts. When overflow occurs, it is important to observe which opening or openings the fluid is overflowing from. Single porous overflow is most often an intraductal papilloma. Porous overflow may be physiologic, pharmacologic, systemic benign disease, or mastopexy. (4) Whether the overflow is spontaneous or spilled after squeezing. The former is mostly pathological, and about 13% of breast cancer patients have a history of spontaneous overflow. Benign or physiological overflow is more common after squeezing. (5) The nature of overflow. Different diseases of the breast have different characteristics when it comes to overflow. For example: ① Milk-like. It is mostly physiological, such as recent after weaning or abortion, and is not a manifestation of cancer. ② Purulent overflow, mostly ductal dilatation and plasmacytoid mastitis. ③ Pale yellow overflow is the most common type of overflow and is seen in almost all kinds of breast diseases, with mastopexy being the most common. Some of them are also intraductal papilloma or breast cancer. Therefore, this is something to be vigilant about. ④ Bloody overflow, which can be of different colors such as bright red, coffee, yellowish, brown, etc. This kind of overflow is a danger sign and should be highly alert, of which 50 – 75% are intraductal papilloma and 15% breast cancer. If the bloody overflow occurs after menopause, 75% are breast cancer. ⑤ Clear watery overflow, colorless and transparent, occasionally sticky, leaving no trace after overflow. This kind of overflow may be a sign of breast cancer and should be further examined. In conclusion, nipple overflow is an important breast symptom, of which 10 – 15% may be breast cancer. Symptoms should be promptly seen in the hospital for cytology examination of the overflow smear. Near infrared breast scan has a positive diagnosis rate of 80–95% for ductal lesions in the areola area. ultrasound and mammogram also have a comparable accuracy rate. Selective lesion ductography is a commonly used test for nipple overflow and is of greater value in the differential diagnosis of benign and malignant with nipple overflow, it also provides the physician with accurate localization of the extent of surgical excision.