MRI done but defect found

Justiny35

My oncologist had me do an MRI of my brain. My brain came back normal but it also said there was an isolated defect about 4mm and my oncologist said your good there is no cancer there. I also had a pet scan from my head to mid thighs which showed no activity in my brain. My oncologist told me that for my cancer which is Diffuse b cell lymphoma i needed xyz treatment so I got a second opinion. This other oncologist stated I need xyz treatment plus methotrexate but because of defect in brain he ordered me to get another MRI done of the brain with a stronger magnet. If there is cancer there than that will determine if he needs to put in an ommaya port or if I can receive intrathecal methotrexate. I am now worried my lymphoma is in the brain. Any thoughts?