Which other than pregnancy can cause nipple discharge ?

Many etiologies: There are many causes of nipple discharge. All need to be evaluated by a physician. Most of these causes are not cancer, but, certainly needs evaluation. Drugs/medications, trauma, hormonal imbalances, are just a few possible causes.

Nipple discharge: Reasons for nipple discharge can include stimulation of the breast, pregnancy, medications, galactorrhea (secretion of milk or similar substance), an abscess or other breast infection, hormonal imbalances (like hypothyroidism), fibrocystic breasts (breasts are very fibrous), blocked mammary duct, breast cancer and intraductal papilloma (non cancerous mass), use of marijuana, anise and fennel.