Nipple discharge is the leakage of fluid from the breast nipple, a common symptom that prompts many people to seek medical advice. While the symptom can be unsettling, it is important to know that most instances of nipple discharge are not related to malignancy. Only a small percentage of cases, approximately 5% to 10%, ultimately lead to a breast cancer diagnosis. Nevertheless, any new or unusual discharge requires a professional medical evaluation to determine the underlying cause and rule out serious conditions.
Specific Colors and Characteristics Indicating Malignancy
The color of the discharge can raise suspicion for cancer, but it is not a definitive diagnostic tool. Bloody discharge, appearing red or pink (serosanguineous), is the color most commonly associated with malignancy. This occurs when blood mixes with fluid passing through the milk ducts, potentially from a tumor.
A clear or watery discharge, medically termed serous, is also highly concerning, especially if it is spontaneous. This fluid signals an underlying issue within the ductal system, even if it does not contain blood. Discharge associated with cancer is typically spontaneous, meaning it occurs without squeezing or physical manipulation.
Discharge that originates from a single duct in only one breast (unilateral and uniductal) is a key feature that increases concern for cancer. This pattern suggests a localized process, such as a tumor, is irritating a specific milk duct. In contrast, discharge from multiple ducts or both breasts is more likely caused by a benign, systemic condition.
Common Causes of Non-Cancerous Nipple Discharge
The vast majority of nipple discharge is benign, often resulting from a physiological or non-cancerous process. Discharge that is milky, white, yellow, green, or brown is usually linked to a harmless condition. Milky discharge, known as galactorrhea, is typically related to hormonal fluctuations, certain medications, or an endocrine disorder causing high prolactin levels.
A thick, sticky, green or black discharge often signals duct ectasia, a common age-related change where milk ducts widen and become inflamed. Yellow discharge may indicate pus from an infection, such as mastitis or an abscess. Non-cancerous growths called intraductal papillomas are frequent causes of bloody or blood-stained discharge.
Discharge that only appears when the nipple is squeezed or stimulated is classified as physiologic and is rarely a concern. This type can be triggered by excessive nipple stimulation, friction from clothing, or normal hormonal changes. If the discharge requires manipulation to appear and comes from multiple ducts, it is less likely to be a serious condition, regardless of color.
Urgent Symptoms and When to Seek Medical Evaluation
While discharge characteristics are important, certain accompanying symptoms are considered “red flags” that mandate immediate medical consultation. The presence of a new, firm lump in the breast or armpit alongside any discharge requires urgent evaluation. A palpable mass significantly increases the likelihood of a cancerous finding.
Any changes to the breast skin or nipple should prompt a rapid visit to a healthcare provider. These changes include dimpling, puckering, persistent redness, scaling, or ulceration. A new inversion or retraction of the nipple, where it turns inward, may also suggest an underlying malignancy.
If the discharge is persistent and occurs spontaneously, regardless of color, it should be investigated promptly, especially in individuals over 40 or in any male patient. Men with any nipple discharge should seek medical attention, as this is always considered abnormal and carries a higher risk of malignancy. Do not attempt to express the fluid, as this can irritate the ducts and hinder the diagnostic process.
Diagnostic Procedures Following Nipple Discharge
A medical workup for concerning nipple discharge begins with a detailed physical examination and medical history to classify the discharge as physiologic or pathologic. The provider identifies the specific duct the fluid comes from and checks for associated masses or skin changes. This initial assessment guides the subsequent imaging plan.
For patients over 40, first-line imaging typically includes a diagnostic mammogram and a breast ultrasound. The mammogram screens the entire breast for masses or suspicious calcifications. The ultrasound provides a clearer view of the area beneath the nipple and the milk ducts, and is often the initial test for younger patients due to breast tissue density.
A fluid sample may be collected for cytology, a microscopic examination to look for abnormal cells, though this test has limited sensitivity. If imaging does not reveal a clear source, a specialized X-ray called ductography may be performed by injecting dye into the affected duct to visualize its structure. If any suspicious area is identified, a biopsy is performed to obtain a definitive tissue diagnosis.