Bloody discharge out of one montgomery gland on right breast. mamo and us negative, pathology inconclusive. does this mean no cancer? what could it be

Unlikely: Montgomery glands are like sebaceous glands , its infection is more like a bad infected pimple is not cancer, but you must see your doctor to treat with antibiotics , if needed drainage (i;d) , and to make sure do not have any serious problem , infection itself is not cancer.

Pathology report?: A common cause of bloody nipple discharge is a benign papilloma. Most times, the duct has to be excised to remove the papilloma both to see if there is cancer present and to stop the bloody discharge. I am not sure what type of biopsy you had (needle biopsy or excision), not sure what inconclusive means. Consider getting a copy of your pathology report and resubmit your question.