Microscopic prolactinoma?

My prolactin levels tested at 66.4 and I have experienced minor galactorrhea. My MRI showed no sign of a tumor. I saw my endocrinologist a couple of days and he was great, he has started me on cabergoline. During my appointment he said he believes I have tumor though it’s probably microscopic since it didn’t show on my MRI. Has anyone had something similar happen? What was your experience?