So the doctor did not suggest gamma knife or tomo therapy? See private message for more info.
Just so you know, you are posting on the layman board, not the expert board. There is another board that is monitored by doctors.
As a parent, you are entitled to more information, good or bad. I am not saying this is bad, just that you need information, which is why you are posting here. I find it sad that the first doctors withheld information from you.
By reading the MRIs and CTs, they can determine for the most part, what type of lesion they are dealing with. For some reason, the first radiologist did not put it in his report but the second opinion gave you his opinion.
The biopsy is the best idea to get the final and of course most accurate information. I hope surgery resolves the tumor.