Well, I don't know how they can say that it is a type that spreads quickly if they don't know what type it is yet.... unless they have suspicions based on the location of the tumor. The most common brain tumor in children is a medullobalstoma, a cancerous tumor in the brainstem. After that is a craniopharyngioma, which is benign, but found much higher in the brain. It is often symptomatic, although not technically cancerous. The symptoms are more related to its location.
Where exactly in the brain is this tumor located? Yes, midline, but down low, like in the brainstem, or up higher, in the midbrain or even higher, in the upper portions of the brain?
Good luck, bro, I hope they can take care of this quickly and you'll be able to get back to your life.