Hi and welcome to HCM. Unless it’s breast milk, any other fluid from the breast is called nipple discharge. Thick/sticky green/black discharge is usually the result of mammary duct ectasia, a problem that’s fairly common in women in their 40s and 50s. It’s an inflammation of one or more milk ducts, much like an internal pimple. It may be painful, but often isn’t. Have your doctor check it to see whether it’s extensive enough that you need an antibiotic. If its light green discharge then it could be galactorrhea, a hormonal imbalance. It should be checked with a doctor not because it’s a danger sign for breast disease, but because it might signal a problem elsewhere in your body, such as an underactive thyroid, or a pituitary disorder. Their may be chances of fibrocystic disease also. I cannot comment on mammogram as u have not specified exactly whats the report of it. But i think its not serious and can be treated. Regards Dr Santosh