A new study has reported that cancer is present in 18% of patients with watery nipple discharge, a group widely considered to be at low risk for breast cancer. The study was designed to investigate the significance of different types of nipple discharge in predicting breast cancer. Nipple discharge is a common symptom among patients seen in breast cancer clinics. The study included 915 patients who presented with nipple discharge as their only symptom and underwent selective surgical duct removal between 1975 and 2008.

A total of 219 patients (23.9%) were found to have carcinoma. Cancer was detected in 100 of 330 (30.3%) patients with bloody discharge and in 42 of 239 (17.6%) patients with watery (serous) secretion. Patients with a thin discharge consisting of serum and blood or colored discharge had the same risk of cancer as the overall study group (i.e., 23.9%). Selective duct removal and pathology were found to have the greatest accuracy with respect to cancer diagnosis. The authors comment that the results confirm the well-established role of bloody secretion as predictor of breast cancer. They conclude, however, that the supposed benign origin of serous, colored or sero-sanguinous discharge is questionable. The high accuracy of cytological exams justifies routine examination of nipple discharge. Selective duct excision can be considered as the diagnostic gold standard.