What do doctors do to tell what kind of tumor someone has on an mri?

Imaging findings: It's the same principle as "how do you know what a table looks like?". Different tumors have different characteristics. Radiologists are trained to recognize what different tumors look like. This is based on size, number of lesions, location, and contrast enhancement pattern.

Well interpretation : Is just that. We take a set of pictures. A specialist looks at the pictures and sometimes can see the problem but sometimes he or she can miss the findings. If we see a mass *tumor on the pictures we then describe it and give a differential of what it might be. But ultimately you and the referring doctor decide if they need to biopsy the mass if they see one.