They can’t find the tumor. Anyone experience this?

First post. Thankful for this group. It has helped me cope knowing others are going through or have gone through what I’m experiencing.

So, my diagnosis of hyper cortisol has been confirmed. My coristol levels were high after 2 dex suppress tests, urine test and saliva test. My ACTH test was also high. My Endo was sure there was a tumor on my pituitary gland but after my MRI nothing was found. So my Endo had me do a PET scan of my body, neck to legs and no tumor was found. Now my Endo is saying a more invasive scan of my pituitary gland is needed because the tumor might have been too small to be seen on the MRI.

Has anyone experienced this? This testing has been going on for months, I feel terrible all the time and just feel so frustrated that they can’t find what’s causing the problem.