A spontaneous nipple discharge not related to lactation or pregnancy is an abnormal finding. It may result from a lesion in the breast (such as papilloma or carcinoma) or from a hormonal abnormality (such as a prolactin-secreting pituitary adenoma).Nipple discharge can be serous (yellow), mucinous (clear and watery), milky, sanguineous (bloody), purulent, multicolored and sticky, or serosanguineous (pink)