Hi,
Most milky discharge is caused by lactation or increased mechanical stimulation of the nipple due to fondling, suckling or irritation from clothing during exercise or activity. Many of these are not relevant in your case.
Drugs or hormones that stimulate prolactin secretion can cause spontaneous, persistent production of milk (galactorrhea). Prolactin is the hormone produced by the pituitary gland that starts the growth of the mammary glands and triggers production of milk. Some pituitary tumors cause excess prolactin secretion that can lead to milky nipple discharge, usually from both breasts (bilateral).
A papilloma is a non-cancerous, wart-like tumor with a branching or stalk that has grown inside the breast duct. Papillomas frequently involve the large milk ducts near the nipple. Of the benign conditions that cause suspicious nipple discharge, approximately half is due to papilloma and the other half is a mixture of benign conditions such as fibrocystic conditions or duct ectasia (widening and hardening of the duct due to age or damage). Suspicious nipple discharge is due to a malignant (cancerous) lesion just ten percent (10%) of the time. Paget's disease of the breast can present with this problem...
Read more here
Given the numerous potential causes you would need further assessment by your Ob/gy as sson as possible,
regards
Dr. Gupta

Edited by Gaurav Gupta on August 13 2007 at 12:09am