Why do you often leak milk?

Patient's question:

Patient Age: Thirty
Main Symptoms: Six years ago, she gave birth to a son, but she occasionally experiences some secretions from her breasts. Recently, especially yesterday, milk-like discharge was drawn out during sexual activity, and a significant amount flowed out. Her menstrual period starts on the 17th and ends on the 22nd. She has no other symptoms in her breasts, such as pain, swelling, or lumps. No gynecological issues have been detected. I am unsure whether this is normal lactation or a symptom of a condition. I need clarification, thank you!
Onset Time: Occurs regularly, but has become more noticeable recently.
Laboratory Test Results:

Doctor's answer:

Hello, during non-pregnancy and non-lactation periods, milky discharge from the nipple is called nipple discharge. Nipple discharge is one of the common symptoms of breast diseases. Statistics show that 3% to 14% of patients visiting clinics with nipple discharge as the primary symptom have breast diseases, with a higher incidence rate than breast lumps and breast pain. If the nipple discharge is unilateral, it is often related to the following breast diseases:
1. Mammary Duct Ectasia: In some patients with this condition, the early symptom is nipple discharge. The discharge is usually brown, occasionally bloody; laboratory tests reveal a large number of plasma cells and lymphocytes but no tumor cells. This condition is more common in women over 40 who are not lactating or postmenopausal. The area around the nipple discharge may have a mass adhering to the skin, usually less than 3 cm in diameter, and the ipsilateral axillary lymph nodes may be swollen, soft, and tender. If infection occurs, the mass may show signs of redness, swelling, heat, and pain.
2. Intraductal Papilloma: This condition is more common in women aged 40 to 50. 75% of the tumor occurs near the nipple, and the tumor is small, pedunculated, and covered with villi, with thin-walled blood vessels, making it prone to bleeding. Tumor cells can be found in the discharge through laboratory tests. Sometimes, when patients examine their breasts carefully, they may notice a cherry-sized mass under the areola, which is soft, smooth, and mobile.
3. Breast Cystic Hyperplasia: This condition is more common in women of reproductive age. In some patients, the nipple discharge may be yellow-green, brown, bloody, or colorless serous. Laboratory tests show no tumor cells in the discharge. This condition has two characteristics:
- It presents with cyclical breast pain, which worsens before menstruation. Mild cases may go unnoticed, but severe cases can affect daily activities.
- Breast lumps are often multiple, appearing in one or both breasts, or localized to a part of the breast. The lumps are nodular, of varying sizes, firm but not hard, not attached to the skin, and have unclear boundaries with surrounding tissues. The lumps may shrink after menstruation.
4. Breast Cancer: Some breast cancer patients have bright red or dark red nipple discharge. Sometimes, clear watery discharge may occur, which is colorless, transparent, occasionally sticky, and leaves no trace after leakage. Cancer cells can be found in the discharge through laboratory tests. The peak ages for this condition are 45–49 and 60–64. The onset is gradual, and patients may notice a breast lump unintentionally, usually located in the inner or outer upper quadrant, painless, and gradually enlarging. In advanced stages, peau d'orange skin changes and satellite nodules may appear. Axillary lymph nodes may be swollen, hard, and fuse together as the disease progresses.
Precautions:
1. Is the discharge true or false? True discharge refers to fluid leaking from the breast ducts. False discharge is common in inverted nipples, where shed epithelial cells accumulate in the, causing a small, watery, bean-like leakage with an odor. Once the inverted nipple is pulled out and the area is kept clean, the "discharge" will disappear.
2. Is the discharge bilateral or unilateral? Bilateral discharge is often physiological. For example, within one year of stopping breastfeeding, many women still produce a small amount of milk. In late pregnancy, some women may produce a small amount of colostrum from both breasts. In a few women, after intense sexual climax, due to highly congested breast blood vessels, breast enlargement, and nipple erection, temporary leakage may occur. During menopause, hormonal imbalance may cause some women to secrete a small amount of milk. These are all physiological conditions and not pathological. However, bilateral nipple discharge can also be pathological, such as hypogonadotropic hypogonadism-hyperprolactinemia syndrome, caused by a pituitary microadenoma. This condition is accompanied by amenorrhea, headache, visual field constriction, and elevated prolactin levels in the blood. A brain CT scan can confirm the diagnosis. Another cause of bilateral discharge is seen in patients with mild breast hyperplasia.
3. Is the discharge from one or multiple holes? The nipple has 15–20 openings for breast ducts. When discharge occurs, observe which one or more openings are leaking. Unilateral discharge is often due to intraductal papilloma. Multiple-hole discharge may be physiological, drug-related, due to systemic benign diseases, or breast hyperplasia.
4. Is the discharge spontaneous or induced? Spontaneous discharge is often pathological, with about 13% of breast cancer patients having a history of spontaneous discharge. Benign or physiological discharge is more often induced.
5. What is the nature of the discharge? The characteristics of the discharge vary depending on the breast disease. For example:
- Milk-like discharge: Often physiological, such as in the immediate aftermath of weaning or miscarriage, and is not a sign of cancer.
- Purulent discharge: Often due to duct ectasia or plasma cell mastitis.
- Light yellow discharge: The most common type of discharge, seen in almost all breast diseases, with breast hyperplasia being the most frequent cause. Some cases are due to intraductal papilloma or breast cancer. Therefore, this requires attention.
- Bloody discharge: Can be bright red, coffee-colored, light yellow, or brown. This is a dangerous sign and should be highly. 50%–75% of cases are due to intraductal papilloma, and 15% are breast cancer. If bloody discharge occurs postmenopause, 75% of cases are breast cancer.
- Watery discharge: Colorless and transparent, occasionally sticky, leaving no trace after leakage. This type of discharge may be a sign of breast cancer and requires further examination.
In summary, nipple discharge is an important breast symptom, with 10%–15% of cases potentially being breast cancer. If symptoms appear, seek medical attention promptly for discharge cytology. Near-infrared breast scanning has a positive diagnostic rate of 80%–95% for ductal lesions in the areola. Ultrasound and mammography also have high accuracy. Selective ductography is a common diagnostic method for nipple discharge, providing significant value for differentiating benign and malignant conditions. It can also help doctors determine the precise surgical excision margins.
I hope this information is helpful to you. Based on your situation and symptoms, it is first considered physiological, but it is recommended to observe carefully and seek medical attention for symptomatic examination and treatment if necessary. There should not be a major problem. Finally, I wish you all the best and happiness. A positive mindset is also a good medicine for smooth progress. Wishing you everything goes well!
Wishing you well!