It is normal for many women to express fluid using external pressure. A small amount of sticky, gray, green, serous, or black viscous fluid could be present. Nipple discharge is the third most common complaint among women after breast pain or a breast mass.
Nipple discharge may be caused by a malignancy. Therefore, it may raise the concern of breast cancer and/or a pituitary tumor. The physician will want to explore further to find the cause.